The long-term real-time water quality monitoring is important for in-depth study of environmental change and ocean farm productivity assessment. This paper designed a remote water quality monitoring system which is based on marine ranching in Xiangshan Port. This system selected the water quality parameters according to the environmental characteristics of marine ranching, and determined the design of each module of lower computer; designed a supporting buoy to carry sensors, power supply, solar panels and other equipment; used C language to compile the network communication program and designed a monitoring software to check the current water quality and the historical data.The system did the experiment in the Jing Lake of Shanghai Ocean University for about 6 months and it was able to upload water quality data in accordance with the set-up program and to display visually by monitoring software. The results showed the effectiveness of the whole system.