There is a problem of uneven power distribution and primary and secondary coupling caused by the introduction of a pure integral module and the fact that primary FM response is relatively slow in the off-grid microgrid using the frequency recovery control of a traditional virtual synchronous generator. Thus this paper proposes a uniform frequency modulation control strategy for a virtual synchronous generator with automatic switching delay, in which the controllable frequency integral feedback loop is used instead of the traditional frequency control loop. With the improved control strategy, the micro-grid inverter can automatically switch between the primary and secondary frequency modulation according to the angular velocity variation, and the frequency recovery and power distribution of the micro-grid can be realized in proportion. A small signal model of the system is established to analyze the stability of the uniform frequency modulation control strategy and the range of parameters is given. The simulation results show that the proposed control strategy can automatically realize the primary and secondary decoupling and the proportional distribution of output power of the virtual synchronous generator on the premise of frequency adjustment without difference. This is beneficial in improving the stability of the system. This work is supported by the National Key Research and Development Program of China (No. 2019YFB1505400).