Due to the large adjust inertia of the diesel generator set (DGS), the quality of power supply would decline when a large load disturbance occurs to the diesel generator system. This paper aims to improve the stability of the diesel generator system voltage amplitude and frequency under impact load conditions using a virtual synchronous generator (VSG) method. Firstly, a mathematical model of DGS is built, the dynamic performances of DGS under a variety of load conditions is analyzed. Secondly, a three-phase energy storage inverter based on VSG control is selected as the parallel power compensator to suppress the system voltage amplitude and frequency fluctuations. Finally, experimental results are given to verify the feasibility and validity of the proposed control strategy.