There are variety of implementations of feeder automation, which can't be verified on the real distribution network. Therefore, it is necessary to design a testing platform to test the feeder automation system. The simulation requirements of distribution network are analyzed, and RTDS is used to build the distribution network model and simulate the fault. A virtual distribution terminal system is proposed, which is used to simulate the operation of a group of distribution terminals. In the structural design process of the virtual distribution terminal system, a topology analysis technology based on CIM is proposed to solve the problem of internal and external data association, the using of virtual switching technology is proposed to solve the problem of data exchange when numerous virtual terminals share one network port. On the basis of the above technology, the testing platform of feeder automation system is designed, which is constituted by RTDS, the virtual distribution terminal system, real distribution terminals and master station system. Finally, the test experiment is carried out on the platform, which verifies the validity of the testing platform. This work is supported by Science and Technology of State Grid Corporation of China (No. 5211DS16000A).