In order to solve testing issues of protective relaying equipment in actual projects, the simulation is made to analyze the microcomputer-based transformer protective relaying equipment by using MATLAB. For transformer differential protection, the analysis is built based on the 110 kV unilateral power two windings transformer power system model. This paper analyzes the relationship between magnetizing inrush current with remanence and closing initial angle, as well as the situation about harmonic contents in inrush current. In view of this situation, the second or third harmonic restraint principle and general percentage restraint differential protection principle are used to study the operating characteristic of differential protection equipment. According to simulation results analysis, parameters for real device are set. In this way, experimental data tested on actual device are obtained. The experiment results show that this method is effective in testing microcomputer-based transformer protective relaying equipment, proving the practical value.