Sun Ji and his identical twin brother Sun Xiang both began their football career playing for Shanghai Cable 02 before the club were taken over by Shanghai Shenhua. They would both graduate to the senior team at the beginning of the 2002 league season and they would both quickly establish themselves as important members within the squad. Sun Ji would personally play in 26 league games and score 2 goals for the team. The following season was to see Sun Ji further establish himself within the team and even help them win the 2003 league title. Unfortunately in 2013 the Chinese Football Association would revoke the league title after it was discovered the Shenhua General manager Lou Shifang had bribed officials to be bias to Shenhua in games that season. Sun Ji continued to be a vital part of the Shanghai team for several more seasons and he attracted attention from Eredivisie champions PSV Eindhoven who invited him and his twin brother, Sun Xiang on trial in November, 2006. PSV coach Ronald Koeman was not satisfied by their performances and did not accept either Sun brother to the PSV team. However, Koeman did not find a satisfactory replacement for left-back over the winter transfer window, so PSV recalled Sun Xiang. Sun Ji returned to Shanghai Shenhua where he continued to be major part of their team.
Hangzhou Greentown
It was confirmed on the website of Shanghai Shenhua that he completed the transfer to Hangzhou Greentown on February 12, 2010. His move would reunite him with his former Shanghai Shenhua manager Wu Jingui and he would quickly establish himself as a vital member within the team as well as also aiding his new club to their best ever finish of fourth and a chance to play in the AFC Champions Leaguefor the first time. Due to spinal injury he retired from playing in 2013.
International career
Sun Ji would make his international debut on February 2, 2007 against Kazakhstan in a friendly game in preparation for the 2007 AFC Asian Cup, which China won 2-1. While he wasn't called up to the Asian Cup squad he would make another appearance for China against Mexico on April 16, 2008 in a 1-0 friendly defeat. This was followed by another friendly on April 23, 2008 against El Salvador in a 2-2 draw.
