Virtual synchronous machine (VSM) technology provides inertia support for power grid by simulating rotor inertia and system damping of drive synchronous machine. However, the dynamic response speed of converter is reduced by damping and inertia. It can not reach the given value quickly and smoothly when the converter need to regulate the output power. In order to solve this problem, an optimal control strategy of load side VSM with adaptive adjust of inertia and damping is proposed in this paper. At different stages of power regulation, the inertia J and damping D of VSM will be regulated autonomously to realize the optimal control of output power. In order to verify the effectiveness of the strategy, the MATLAB/Simulink model of VSM is established and the simulation experiment is carried out. Compared with the traditional control method, the active power regulation speed of the synchronous machine is faster, the fluctuation and overshoot in the regulation process are smaller and the dynamic regulation performance is better.