Santos Weldon (45) and Tianbao Cao (58) shocked their second-placed hosts who could only reply through their Brazilian vice-captain Eleilson (67).
The defeat ended Jiangsu's perfect home record, after they had won their previous four games at the Nanjing Olympic Sports Centre, and left them four points off the top.
Hangzhou Greentown were 2-1 winners as they toppled Liaoning. Gang Feng (six) and Wei Du (31) sent them ahead before Valtko Grozdanoski pulled one back in first-half injury time.
Shanghai Shenhua played out a goalless draw at home to Shanxi Zhongxin.