Choi, who became Seoul's full-time head coach in 2012, also guided the team to the K League title that year and a runners-up finish in the 2013 AFC Champions League.
He joins compatriots Chang Woe-ryong (Chongqing Lifan), Lee Jang-soo (Changchun Yatai), Hong Myung-bo (Hangzhou Greentown) and Park Tae-ha (Yanbian Funde) in China's top flight.
Jiangsu currently sit third in the championship, four points behind leader Guangzhou Evergrande.
(Reporting by Ian Rodricks in Bengaluru; Editing by Peter Rutherford)
