With the development of numerical protection relay and the communication technology based on the IEC 61850 standard， research on platform environment is becoming more and more important. Not only should the platform guarantee the performance and stability of the devices， but it should be convenient for upgrading and product function maintenance. A kind of numerical protection relay simulator as well as its implementation is described， which uses software to simulate the protection relay operating and testing environment. This can enable the development and test to be implemented on one PC， greatly enhancing the development efficiency and reducing development cost while ensuring the R&D quality during product function improvement.