Compact phase-change energy storage refrigeration system, which cools the short-time high-power electronic appliances directly, is an important thermal management system. The effective control of the temperature and pressure in the working process is the main problem to be solved during the application of the system cooling a high power heat source. In this work, theoretical analysis, design and calculation of the liquid accumulator for the energy storage refrigeration system of 10 kW heat source with NH3 as the refrigerating working medium was studied theoretically, and the experimental platform for the experimental research was also built up. The results showed that the liquid accumulator, as the constant pressure equipment of the system, played a role of replenishing and storing the working medium of the storage system during the system start-up and operation. The pressure fluctuation in the accumulator was related to heat addition, evaporation temperature, volume of reservoir and initial system pressure. The temperature fluctuation of the heat source during operation was only 1.2℃, as the volumetric ratio of accumulator to system of 1.48. The coupled working characteristics of the condensing reservoir and the accumulator can restrain the temperature and pressure fluctuation of the system, when the heat source was disturbed.