Abstract: When the master micro-source of microgrid switches from P/Q control to u/f control, the system voltage and frequency instability will be caused by the same parameters of inner loop. Therefore, the parameter switching control strategy of inner loop based on master micro-source is proposed. The general model of control system for master micro-source is established. Considering the different expected control performance, the parameters of inner loop for P/Q control and u/f control are designed based on second-order system and third-order system respectively. The parameters of inner loop PI controller are switched while microgrid is switched from grid-connected operation to islanded operation. This control strategy can not only realize rapid target tracking when microgrid operation mode are switched, but also improve the stability and reliability of the system.Finally, a simulation example is given to verify the proposed control strategy.