Different microsources have different frequency regulation functions when the microgrid is islanded. The droop con-trol inverters can distribute the disturbed power among the microsources according to the operation demand; however， the steady state frequency often deviates from the rated value because of the droop characteristics. By adding the integral control to the droop control algorithm， the inverter can regulate the frequency without frequency error; but the disturbed power is under-taken only by the microsources which have the integral control. The transfer function of the inverter is designed based on the zero-error frequency regulation control strategy， and then the frequency restoration function is verified through mathematical derivation. Furthermore the power distribution strategies of the microsources with zero-error frequency regulation functions are studied. Finally， a simple microgrid is modeled based on MATLAB-Simulink platform， and the simulation results are coinci-dent with the theoretical analysis results， which validates the validity and effectiveness of the above conclusions.