At the
2004 Athens Olympics, when he was only 17, Wu Peng made the 200 m butterfly final and became the only Chinese swimmer to finish in the top eight at the games. It was only Wu's first Olympics, and the team was satisfied with his performance. At the
2006 short course World Championships in Shanghai, Wu won the 200 m butterfly in a championships record. He also won the bronze medal at the
2005 World Long Course Championships in
Montreal, and the silver behind
Michael Phelps at the
2007 World Long Course Championships in
Melbourne, both times at 200 m butterfly. At the
Beijing Olympics, he carried the nation's hopes for a breakthrough in swimming. Although making it to the finals, he managed a joint fourth with the New Zealand swimmer
Moss Burmester. He suffered an injury in 2009 and could not make it to the World Long Course Championships to try for the podium once again. Wu himself has said that if he were to medal in the London 2012 Olympics, he would consider his career to have been full and satisfying. Wu Peng defeated Michael Phelps in the 200
fly in consecutive events, at the Michigan Grand Prix and Charlotte UltraSwim, in 2012 ending Michael Phelps' streak of 60 wins in nearly 9 years. In 2023, Wu staged a comeback at the Chinese Spring National Championships and the Chinese National Championships, a decade after his retirement. His aim was to take part in the
2023 Asian Games which would be held in his home city of Hangzhou. However he failed to qualify after finishing 5th in the 50m butterfly event. ==Major achievements==