Concerning the problem of combination explosion which was caused by the combinations of all kinds of foundation software, the methods of combinatorial design were studied, and an approach based on combinatorial design was proposed to choose integration testing combinations that cover the interaction between foundation software. Foundational software platform was composed of many types of foundational software, and each type of foundational software had different brands and different versions. Each type of foundational software was expressed as a variable factor, and software products of different brands were viewed as variable values, then foundational software platform could be regarded as a multifactor system. The corresponding orthogonal array or the covering array based on orthogonal array was constructed. Integration testing combinations were chosen with the help of orthogonal array and the covering array. The results of the cases indicate that the number of the testing combination can be effectively decreased, and the pairwise test coverage is ensured.