According the stiffness of bearing plate, the deformation test of bearing plate method is divided into rigid bearing plate method and flexible bearing plate method.Adaptation range of the two tests are stipulated according to regulations. To complete and comparatively complete rock, the two tests may be adapted. It is controversial which kind of test method is adapted in testing complete and comparatively complete rock masses. The article does research in theory model, in-situ experiment and numerical simulation. The research results show that the flexible bearing plate method is suitable to test the deformation of complete and stiff rock mass.