Cao Yongjing was promoted to Chinese Super League side Guizhou Renhe's first team squad in 2015.[1] On 14 March 2015, he made his Super League debut in a 2-0 away defeat at Jiangsu Sainty, coming on as a substitute for Magnus Eriksson in the 76th minute.[2] Unfortunately he would be part of the team that was relegated at the end of the 2015 Chinese Super League season.[3] He would remain loyal towards the club as they moved locations, renamed themselves Beijing Renhe and gained promotion back into the top tier at the end of the 2017 league season.[4] On 15 April 2017, he scored his first goal for the club in a 2-1 home win against Meizhou Hakka.
On 10 March 2018, he scored hist first Chinese Super League goal in a 2-1 away win against Tianjin Quanjian. At the end of the 2019 Chinese Super League he would experience another relegation with the club.[5]
Beijing Guoan
On 9 February 2021, Cao joined city rivals Beijing Guoan on a free transfer following the disbandment of Beijing Renhe, and was given the number 37 shirt.[6] On 24 April 2021, he made his debut in the opening league game against Shanghai Shenhua that ended in a 2-1 defeat.[7] On 4 January 2022, he scored his first goal for the club in the final league game of the season against Shenzhen F.C. in a 1-0 victory.[8]
After returning to Guoan following a loan spell at Yatai, Cao reached his career peak during the 2024 season, where he scored a career-high 8 goals in only 15 appearances, which paved his way into being selected by the national team.