Template: Infobox Badminton Player / Maintenance / English
Cai participated for China at the 2004 Olympics with his partner Fu Haifeng in the men's doubles. They had a bye in the first round and in the second round Keita Masuda and Tadashi Ohtsuka from Japan. In the quarterfinals subject Cai and Fu Jens Eriksen and Martin Lundgaard against Hansen from Denmark with 3:15, 15:11, 15:8.
Cai won in 2005 with his partner Fu Haifeng in the men's doubles at the German Open. Cai Yun won together with his partner Fu Haifeng on 24 September 2006, the men's doubles final of the Badminton World Championships in Madrid. Moreover, the two were in addition to various quarter-, half - and finals at the Chinese Taipei Open and Macau Open the winners. Cai Yun 2007 was a member of the Chinese team that successfully defended on June 17 the Sudirman Cup against Indonesia.
Also at the 2008 Olympics in his home country Cai again took part in the men's doubles with Fu Huaifeng. This time they lost only in the finale Markis Kido and Hendra Indonesians Setiawan and won the silver medal.
In 2012 he started again at the Olympics, where she won gold in men's doubles.