DIgSILENT PowerFactory, a simulating software, is exclusively devised for electric power system analysis and control. Equipped with a rich electric component model, it has brought great convenience for research and study on power system with distributed generation. This paper introduces the modeling principle, general framework, and various functional modules in the simulation of relay protection based on DIgSILENT. By illustrating overcurrent protection and distance protection simulation, this paper presents the process of the application of DIgSILENT in relay protection simulation. And the effectiveness and correctness of relay protection simulation by using DIgSILENT is proved, demonstrating the advancement of the software in this field. This work is supported by National Key Research and Development Program of China (No. 2017YFB0902801).