A hyperspectral system for real-time observation of ocean color is developed. The system includes three main units: an optical-fiber-based hyperspectroradiometer for in situ measurements of upwelling radiance and downwelling irradiance both at sea surface and at underwater depths, a moored buoy platform suitable for loading the hyperspectroradiometers and other auxiliary sensors, and an electrionic system for data acquisition and real time data communication. A six-channel optical fiber spectroradiometer is designed, which can simultaneously measure parameters at different depths. The large dynamic range of the spectroradiometer is achieved by auto-adjusting the integration time of CCD array detector. The use of optical fiber makes it possible to minimize the collector of sensor, and thus the instrument self-shading effect is reduced. An auto-driving mechanical brush is designed for optical sensor, which prevents the sensors from bio-fouling and enables the sensors to work well underwater. The characteristics of the system were tested in laboratory, and the buoy was deployed in near-shore waters for 36 days in situ experimental testing. Experimental results show that, the errors for the optical parameters are within ±5%, and the buoy has a good stability at high sea state conditions, and the data acquisition and electronic communication system is reliable and effective.