In the engineering application of a dispatcher training simulator（DTS）， testing of the secondary system simulation module always consumes a considerable amount of time. It is then desirable to improve efficiency and quality of the process by automatic testing tools. Because general automatic testing tools can not be directly applied to testing of the secondary system simulation module， a special testing tool is designed and implemented. Its software structure and functions are presented. The structure of the testing database which supports parallel testing on several nodes is also introduced. The automatic generating and running of testing cases are illustrated. The testing tool has been used in the engineering application of DTS. The engineering quality is improved and the engineering duration is significantly reduced. It also facilitates increased range of testing cases. These validate the effectiveness of the automatic testing tool.