In June 195 BC,
Emperor Gaozu died and was succeeded by Liu Ying, who became historically known as
Emperor Hui of Han. Lü Zhi was honoured by Emperor Hui as
empress dowager. She exerted more influence during the reign of her son than she had when she was empress, and she became the powerful and effective lead figure in his administration.
Roles in the deaths of Concubine Qi and Liu Ruyi Lü Zhi did not harm most of Gaozu's other consorts and treated them according to the rules and customs of the imperial family. For example, consorts who bore male children that were instated as princes were granted the title of "Princess Dowager" () in their respective sons' principalities. One exception was
Concubine Qi, whom Lü Zhi greatly resented because of the dispute over the succession between
Liu Ruyi (Qi's son) and Liu Ying. Liu Ruyi, the Prince of Zhao, was away in his principality, so Lü Zhi targeted Concubine Qi. She had Qi stripped of her position, treated like a convict (head shaved, in
stocks, dressed in prison garb), and forced to do hard labour in the form of milling rice. Lü Zhi then summoned Liu Ruyi, who was around the age of 12 then, to Chang'an, intending to kill him together with his mother. However Zhou Chang (), the chancellor in Liu Ruyi's principality, whom Lü Zhi respected because of his stern opposition to Emperor Gaozu's proposal to make Liu Ruyi crown prince, temporarily protected Liu Ruyi from harm by responding to Lü Zhi's order that, "The Prince of Zhao is ill and unfit for travelling over long distances." Lü Zhi then ordered Zhou Chang to come to the capital, had him detained, and then summoned Liu Ruyi again. Emperor Hui tried to save Liu Ruyi by intercepting his half-brother before the latter entered Chang'an, and kept Liu Ruyi by his side most of the time. Lü Zhi refrained from carrying out her plans for several months because she feared that she might harm Emperor Hui as well. One morning in the winter of 195–194 BC, Emperor Hui went for a hunting trip and did not bring Liu Ruyi with him because the latter refused to get out of bed. Lü Zhi's chance arrived, so she sent an assassin to force poisoned wine down Liu Ruyi's throat. The young prince was dead by the time Emperor Hui returned. Lü Zhi then had Concubine Qi killed in an inhumane manner: she had Qi's hands and feet chopped off, eyes gouged out, ears burned, nose sliced off, tongue cut out, forced her to drink a potion that made her mute, and had her thrown into a
latrine. She called Qi a "human swine" (). Several days later, Emperor Hui was taken to view the "human swine" and was shocked to learn that it was Concubine Qi. He cried loudly and became ill for a long time. He requested to see his mother and said, "This is something done not by a human. As the empress dowager's son, I'll never be able to rule the empire." From then on, Emperor Hui indulged himself in carnal pleasures and ignored state affairs, leaving all of them to his mother, and this caused power to fall completely into her hands.
Treatment of Emperor Gaozu's other sons Around the winter of 195–194 BC,
Liu Fei, the Prince of Qi, Emperor Gaozu's eldest son born to Lady Cao (), visited
Chang'an and he and Emperor Hui attended a banquet hosted by the empress dowager. Emperor Hui honoured Liu Fei as an older half-brother and treated the latter respectfully. Lü Zhi felt offended and secretly instructed her servants to pour a cup of poisoned wine for Liu Fei, and then toasted him. Just as Liu Fei was about to drink the wine, Emperor Hui realised his mother's intention and grabbed Liu Fei's cup as if he would drink from it. Lü Zhi immediately jumped up and knocked the cup out of Emperor Hui's hand. Liu Fei then offered to give up an entire
commandery from his principality to Lü Zhi's daughter,
Princess Yuan of Lu. Lü Zhi accepted the offer and allowed him to leave. Lü Zhi also played a role in the death of another of Gaozu's sons,
Liu You, the Prince of Zhao. Liu You married Lü Zhi's niece but was caught having an affair with another woman, so Lü Zhi's niece reported to her aunt that Liu You was plotting a rebellion. Lü Zhi summoned Liu You to
Chang'an and had him imprisoned and deprived of food. Liu You was afraid of committing suicide and eventually starved to death, in February 181 BC. Lü Zhi then transferred another of Gaozu's sons, Liu Hui, the Prince of Liang, to Zhao, and forced him to marry a daughter of Lü Chan. The Lü clan grabbed the authority of Zhao and oversaw Liu Hui, thus making Liu Hui feel restricted. Princess Lü had a favored concubine of Liu Hui poisoned to death. Liu Hui was distressed and committed suicide in fear in July 181 BC. For the matters above, Lü Zhi was criticized for "having murdered three princes of Zhao".
Marriage proposal from Modu In 192 BC, Lü Zhi received a marriage proposal from the
Xiongnu chanyu Modu, who wrote as follows in a letter meant to intimidate and mock her: I'm a lonesome ruler born in marshes and raised in plains populated by livestock. I've visited your border numerous times and wanted to tour China. Your Majesty is now alone and living in solitude. Since both of us are not happy and have nothing to entertain ourselves, I'm willing to use what I possess to exchange for what you lack. Lü Zhi was infuriated at the rude proposition, and in a heated court session, her generals advised her to rally an army and exterminate the Xiongnu immediately. As she was about to declare war, an outspoken attendant named
Ji Bu pointed out that the Xiongnu army was much more powerful than the Chinese. At Ji Bu's words, the court immediately fell into a fearful silence. Rethinking her plans, Lü Zhi rejected Modu's proposition humbly, as follows: Your Lordship does not forget our land and writes a letter to us, we fear. I retreat to preserve myself. I'm old and frail, I'm losing hair and teeth, and I struggle to maintain balance when I move. Your Lordship has heard wrongly, you shouldn't defile yourself. Our people did not offend you, and should be pardoned. We've two imperial carriages and eight fine steeds, which we graciously offer to Your Lordship. However, she continued implementing the
heqin policy of marrying Han princesses to Xiongnu chieftains and paying tribute to the Xiongnu in exchange for peace between both sides.
Emperor Hui's marriage to Empress Zhang Yan In 191 BC, at Lü Zhi's insistence, Emperor Hui married his niece
Zhang Yan (Princess Yuan of Lu's daughter) and made her empress. They did not have any children. It was alleged that Lü Zhi told Zhang Yan to adopt eight boys and have their mothers killed. There is uncertainty whether these children were Emperor Hui's; the traditional view is that they were not, while modern historians believe that they were born to his concubines. == As empress dowager: grandmother and an acting emperor==