The advantages of aquaculture with closed cage are zero emission, no pollution and environment friendly; while the disadvantages are the proneness of the water quality deterioration and the huge energy consumption for water exchange and sewage. In order to reduce energy consumption and ensure the normal operation of the equipment, a hybrid power supply system of solar energy-mains-diesel generator has been developed. Based on the charging and discharging characteristics of batteries, the intelligent solar charging and discharging control and protection is achieved by using the technology of Maximum Power Point Tracking (MPPT) and Digital Signal Processing (DSP); and an orderly hybrid power supply is achieved by using dual power Automatic Transfer Switching (ATS). The average monthly solar power capacity is 250KWh and the average daily power supply is 8.3KWh, which meets the requirements of the average daily load consumption of 6.6 ~ 8.8KWh. The results showed that, the power is supplied by the solar energy on sunny days and the power is supplied by the battery (discharge for 3 to 4 hours upon full charge), mains and diesel generator in turn during continuous rainy days. The energy saving effect will be more obvious with the improvement of the solar energy system.