To overcome the shortages of the analysis of the differential protection characteristic in the differential currents vs. resistant currents plane and complex plane at present, this paper proposes a novel method, which analyzes the differential protection characteristic in polar coordinate. The representation of fault component current differential protective criterions in polar coordinate is presented, and the comparison of characteristics of fault component current different criterions is described with this method which provides basis for the actual application. What’s more, this method is convenient to analyze the influence on differential protection when both amplitude and phase of currents are changing. Sensitivity coefficient is introduced to contrast characteristic of criterions in both internal and external faults. The simulation results from the faults in 110 kV line by using PSASP are consistent with that of the theoretical analysis.