In 2001, Xu began training for
mixed martial arts (MMA) and
Muay Thai. In 2003, Xu fought against
Brazilian jiu-jitsu practitioner,
Andy Pi (毕思安) in a televised bout. During the fight, Xu broke Pi's forearm with a kick, but Pi managed to eventually get Xu to the ground where he won via armbar submission. Pi would later go on to found the first professional MMA promotion in China,
Art of War Fighting Championship. In 2004, Xu tore his
Cruciate ligament in a football match and had to get it reconstructed at
Peking University Third Hospital. It was considered a partial disability which as a result led him to transition to full time coaching in 2005. Some in China believe that kung fu masters have supernatural powers, and self-described masters, including
Wei Lei, were known to make such claims online. After the fight went viral, there was significant blowback on social media where he was accused of disparaging Chinese culture, and his family received death threats. Beverage tycoon
Chen Sheng offered over a million US dollars to any traditional tai chi fighter who could beat Xu. Following this, police stopped a fight against another self-proclaimed
tai chi master, Ma Baoguo, who allegedly called them in, and Xu was banned for organizing tournaments at his gym. However, Xu continued to fight self-proclaimed tai chi masters. In 2018, Xu was notoriously injured fighting in a series of sparring matches at a Chinese MMA gym. During his fourth round, pitted against Yan Shuaiqi, Xu received a series of knees to the face and was left with a fractured skull and needing 26 stitches around his eyebrow. Yan later apologized for injuring him, but Xu assured he did not care, stating, "if traditional martial artists could beat me the way these MMA fighters did then I'd be so happy". During this year, Xu would also receive vocal support from
Shaolin abbot
Shi Yongxin, who claimed that Xu's actions against fake kung fu artists were good for the traditional art forms. Xu was sued for defamation in 2019 for calling
tai chi Grandmaster
Chen Xiaowang a fraud, and the Chinese court ordered him to pay Chen approximately US$60,000 in damages and to apologize for seven consecutive days on social media. After refusing to do this, his
credit rating was lowered to the point where he could not rent, own property, stay in certain hotels, travel on high speed rail, or buy plane tickets. The restrictions were lifted after he paid US$40,000 in both legal fees and the cost of placing the apology. In May 2019, Xu defeated another martial artist, but was only able to do so wearing
clown makeup to hide his face and by fighting under a pseudonym. It took him 36 hours to reach the fight location due to his low credit score, and Chinese search engines reportedly had stopped listing him. Later that year, Xu had to wear
Peking Opera face paint and cover his back tattoo during his match with Japanese kickboxer
Yuichiro Nagashima so that the fight which took place in Thailand could stream in China. The fight was hosted under kickboxing rules in the first round and mixed martial arts in the second, and saw Xiaodong eventually winning by TKO by
ground and pound in the second round. By defeating Nagashima, Xu believed that he could pressure kung fu fighter
Yi Long, whom Xu had claimed has rigged competitions, to face him in a match. In November 2019, an
Iron Palm master threatened to break Xu's arm in a fight, but apologized and backed down after Xu accepted and suggested putting 200,000 yuan on the outcome. In July 2020, the Chinese Wushu Association urged practitioners to refrain from calling themselves "master". This was interpreted by Bloody Elbow (MMA news site) and Radii China as being in response to Xu's complaints about "kung fu fakery". In November, Xiaodong defeated Chen Yong, a tai chi master who had challenged him in 2018, in only 10 seconds. ==Political views==