Based on microgrid features， different control strategies are designed for two operation modes of microgrid. When the microgrid is on isolated island operation mode， distributed generation units adopt voltage source inverter control， using voltage amplitude and phase angle droop control to share load power according to predetermined proportion. This droop control can provide better frequency support than voltage amplitude and frequency droop control. When the microgrid is on grid-connected operation mode， distributed generation units adopt PQ control so as to output power according to given values. Microgrid operation modes can achieve seamless transition by using synchronization controller corresponding to voltage amplitude and phase angle droop control. Microgrid transition between operation modes and comparison between two kinds of droop control when microgrid operates on isolated island operation mode are analyzed. MATLAB/Simulink simulation shows that voltage amplitude and phase angle droop control strategy is feasible and effective.