Abstract: Combining with the testing experiences of European Train Control System (ETCS) and aiming at the requirements specification of CTCS-3 level train control system, this article researched on the automatic testing method of CTCS-3 level train control system based on Testcase Designer. Testcase Designer is mainly applied in modularizing test case to optimize the writing process, form test sequence which could satisfy the requirement of test platform, provide key data points for the execution of test program. At the same time, Testcase Designer could be used for storage, exporting and publishing. The configuration information of key input/output interface in test case (e.g., BTM, TIU, RTM, etc.) were implemented through configuration file. The scenario of RBC handover was taken as an example to write the test case of this scenario with Testcase Designer. The research results showed that Testcase Designer integrated feature, reference requirements and test steps as well as the written test case were reasonable.