Power sharing between inverters and microgrid modeling and stability analysis are hot research field in microgrid research. The line impendence is an important parameter to improve the power sharing accuracy, and modeling the microgrid system. Line impedance measure methods have been discussed in several papers. This paper summarized and analyzed each of these methods, identified their advantages and weaknesses, then describes a power variation method for estimating the line impedance of microgrid. Simulation results reveal the correctness and good accuracy of the proposed method.