This paper expounds the status of real time digital simulation, analyzes the pros and cons of real time simulator (RTDS), and puts forward a method for processing the test of equipment. Based on this, the paper introduces an automatic testing system for real time simulation combined with RTDS, Visual Basic# codes and databases. Exerting the professional platform of RTDS, strong compatibility of Visual Basic and standard storage feature of database, and considering the reliability constraints, it establishes a man-machine interface and figures out a method for processing the test of equipment. The accuracy of the system is provided by the line differential protection test. It shows that the system can realize the function of automatic testing, balance the reliability and flexibility, and is valuable to be popularized.