The analysis of the current transformer transient saturation characteristic and its impact on differential current protection is an urgent problem to be solved. A simulation platform for analyzing the transient characteristic of the current transformer is introduced. The actual operating scene can be constructed in this platform. A variety of complex transient process in the power system can be simulated. The class P, PR and TPY current transformer model can be selected for analyzing the transient characteristic of the current transformer. This platform can achieve the analysis on the current transformer transient characteristic and its impact on the differential protection. The dynamic test and practical application prove the accuracy and the effectiveness of this platform.