Abstract: Shanghai states the construction of“Four Centers”in the“Twelfth Five- Year Plan”, improving the development of Shanghai marine industry. The structure of Shanghai marine industry has achieved the transition from the“ One-Two-Three”structure to the“Three-Two-One”structure. Shanghai marine industry provides a broad space for the regional employment. At the marine environment aspect, the ecosystem situation of the Yangtze River estuary is still in a sub- healthy condition. This paper analyzes the development of Shanghai marine industrial structure, the correlation of Shanghai main marine industries and the development decision-making for Shanghai marine industries using the Gray System Theory. It proposes to continue to optimize the Shanghai marine industrial structure, focus on the development of leading industries and advantage industries, foster the marine industrial groups, and enhance the hightech industrial development