Yang Xu would make his first senior appearance for Liaoning Whowin on 16 April 2005 in a league match against Shanghai Shenhua, which they lost 1-0. Despite this loss, his performance was good enough to see him recalled in the next league game against Wuhan Huanghelou, however this was to again end in a 1-0 defeat. Liaoning's performances would improve throughout the season and Yang Xu would eventually score his first league goal against Shenzhen Jianlibao on 15 May 2005 in a 3-1 league win. By the end of the 2005 season, Yang Xu would eventually score 3 league goals in 11 appearances and see Liaoning FC finish the league season in middle of the table in tenth.
The following season would see Yang Xu continue with establishing himself with the Liaoning Whowin team by making a further 20 league appearances and scoring 3 goals, however most of these came from the substitute bench during the season. By the 2008 season, Yang Xu was still a squad player trying to establish himself as the main striker within the team and while he scored three more goals during the campaign he was unable to help Liaoning avoid relegation at the end of the season. Staying with Liaoning, Yang Xu was promoted as their first choice striker at the beginning of the 2009 league season and would repay Liaoning with 15 league goals in 22 appearances, making him the second best goalscorer in the league. His goals would aid Liaoning to win the division title and immediate promotion back into the Super League.
After an impressive start to the 2009 season with Liaoning Whowin, Yang Xu was called up to the senior national team despite playing for a team in the second tier. He would be tried out in friendlies before he was given his chance to play in a competitive game for qualification into the AFC Asian Cup in a game against Vietnam on 17 January 2010 where he also scored his debut goal. On 30 March 2011, he scored twice as China beat Honduras 3-0 while on 23 July 2011, he scored his first international hat-trick against Laos.