|Date of birth||October 17, 1984|
|Place of birth||Shanghai, China|
|Height||1.86 m (6 ft 1 in)|
|* Senior club appearances and goals counted for the domestic league only and correct as of 22 October 2016.
Shanghai Shenhua and Education
Zhou Yajun began his football career with the various Shanghai Shenhua youth teams and took part in the squads that trained in Brazil, however instead of immediately continuing with his football career Zhou Yajun would instead continue with his studies and go to Donghua University where he still played football as a goalkeeper. Once he had completed his studies he was allowed to return to Shanghai Shenhua and by the 2006 Chinese Super League season he would start his professional football career as their third choice goalkeeper. His league debut would come on July 16, 2006 against Qingdao Zhongneng in a 2-0 win. Surprisingly he would find himself continuing to play in goal due to injury and suspensions to the other goalkeepers and by the end of the season he had played in 12 league games. Zhou Yajun's progression within the Shanghai Shenhua's football team was short lived when they merged with local football team Shanghai United F.C. and with the influx of players he found himself immediately dropped from the newly formed team throughout the 2007 league season.
Zhou Yajun was surplus to requirements and was allowed to leave Shanghai Shenhua at the end of the 2007 league season and by the beginning of the 2008 Chinese Super League season he joined Henan Construction. He would make his debut on their first game of the season on April 5, 2008 against Liaoning Whowin F.C. in a 3-3 draw. After that game he would become their first choice goalkeeper throughout the season. While he aided Henan to a respectable 10th within the league he was dropped in favour of new goalkeeper Zeng Cheng by new Manager Tang Yaodong at the beginning of the 2009 Chinese Super League.
Statistics accurate as of match played 22 October 2016. 
|Club performance||League||Cup||League Cup||Continental||Total|
|China PR||League||FA Cup||CSL Cup||Asia||Total|
|2006||Shanghai Shenhua||Chinese Super League||12||0||1||0||-||2||0||15||0|
|2008||Henan Construction||Chinese Super League||28||0||-||-||-||28||0|
|2013||China League One||29||0||0||0||-||-||29||0|
|2014||Chinese Super League||16||0||1||0||-||-||17||0|
|2016||Shenzhen||China League One||25||0||0||0||-||-||25||0|
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- "周亚君". sodasoccer.com. Retrieved 2012-09-26.
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- "奥利萨德贝梅开二度 河南3-3逼平辽宁 视频 评". sports.sohu.com. 2008-04-05. Retrieved 2012-09-26.
- 深圳官宣徐亮等三将加盟 at sports.sina.com 2016-02-03. Retrieved 2016-02-03
- 周亚君 at sodasoccer.com Retrieved 2014-11-01 (Chinese)