Jiang Jing was from Tanzhou, Hunan. He once failed in an imperial examination, and after that he shifted his focus from books to martial arts. He was an expert in martial arts, mathematics and in deploying troops, so he was nicknamed the 'Magic mathematician' (神算子).
Once, Chao Gai led the Liangshan heroes to storm the execution ground in Jiangzhou to rescue Song Jiang and Dai Zong. On their way back, the heroes passed by Huangmen Mountain, where Jiang Jing, Ou Peng, Tao Zong-wang and Ma Lin. They stopped Song Jiang and wanted to join the Liangshan band, which Song agreed.