The water quality of the aquaculture is complex and easily mutated. The spectrum data of water can reflect the mutation directly. A spectrum observation system for aquaculture water is designed to provide data basis and scientific ground for spectrum analysis of aquaculture water and evaluation of water quality. A real-time and automatic spectrum observation system is constructed based on the high-precision optical sensor, Flash storage technology, GPRS and RS485 wireless data transmission technology to observe the spectrum data of specific bands in aquaculture pond. Through continuous observation of samples in 5 ponds, after regression analysis with simultaneous observation data of ASD spectrometer in the bands of 680nm, 700nm and 769nm as standard value, and quantitative analysis of system performance index, it is obtained that the accuracy of the observed data is above 98%, and the system performance is up to standard. The result shows that, for spectrum observation of aquaculture water in specific band, this system could take the place of artificial spectrometer for observation, realize remote and real-time data observation, reduce tedious observation procedure, economize on manpower and material resources, and avoid error caused by artificial observation.