After two silver medals at the 1989 Asian Championships and the Asian Games in 1990 Xu Demei won in the javelin at the Asian Championships in 1991. At the World Athletics Championships 1991 in Tokyo Xu Demei threw in the first attempt of the finals with 68.78 meters personal best. The German world record holder Petra Meier came to her with 68.68 meters, although very close, but could not surpass the Chinese. This Xu Demei won a complete surprise the world title. Just a week earlier Huang Zhihong had won in the shot put throw the first title for a Chinese.
At the 1992 Olympics in Barcelona Xu Demei threw 59.98 meters in qualifying and could not as Fourteenth qualify for the final.
At a height of 1.74 m Xu had a competition weight of 75 kg.