With 22 years of Yan Zi won in 2005 in Guangzhou her first and only single title on the WTA Tour. In January 2006, she reached for the first time the top 100 in the world tennis rankings and then climbed up to rank 72 Due to poor results it fell in February 2007 back to Rank 262. With very good results in the rest of the year, she returned in the top 100. Mainly through their results at the Rogers Masters in Canada, where they only lost in the semifinals of the former world number one Justine Henin with 3:6 and 0:6. In May 2008, Yan Zi reached Rank 40 their record in the WTA world rankings.
In doubles, she could come up with better results. In the double - World ranking it reached in July 2006 with 4th place their highest position. With her (until 2008) permanent doubles partner Zheng Jie won 2006 two Grand Slam tournaments, the Australian Open and the Wimbledon Championships. The 2006 season was for the Chinese with a total of six titles (including two Grand Slam successes ), the most successful on the tour.
The year 2007 was a little worse. She won six doubles titles, including the scoring at the Masters Series tournament in Charleston. At the U.S. Open she succeeded in 2008, Zheng Jie, with which it has hitherto win eleven victories on the Tour, the quarter-finals. They lost there to eventual tournament winners of Cara Black and Liezel Huber.
At the Olympic Games in Beijing in 2008, it reached the semi-final Zheng Jie, but it lost to Anabel Medina and Virginia Ruano 4:6, 6:7. In the third place match against Kateryna Bondarenko and Alyona, she won the bronze medal with Zheng Jie.
In May 2011, she was disqualified in the individual competition twice already out in qualifying. In Rome, she joined her first round defeat in a double for the time being the last time to a match on the tour.
On January 17, 2012 Yan Zi mother has become. In September 2012, she returned to the tour since 2013, it only plays in the doubles competition.