Abstract: According to the characteristics of hardware and interlocking software of computer interlocking system, this paper introduced the purpose and procedure of software testing, the equivalence class partition method in black box testing and the fault tree analysis method used in security testing. Based on the interlocking software testing of the test platform composed by the test software, interlocking software and station signal equipment simulation system, and on the basis of the interlocking software black box testing coverage criterion, this paper introduced the detailed process and test flow of writing test cases with the equivalence class partition method and using the fault tree analysis method. At the same time, the python pseudo code was used to implement the test cases of “route selection”. The above method was used to demonstrate the importance of black box testing in the logical function of computer interlocking software.