Abstract: Deep rock mechanics is the theoretical basis of deep engineering practice, and implementing shear strength tests of rocks under the deep environment is critical for investigating deep rock mechanic behaviors. A set of fixture is designed for direct shear tests applying to cylindrical specimens. Together with MTS 815 rock mechanics test system, the fixture can realize a series of shear tests under high temperatures and pressures, i.e. shear tests, shear creep tests and shear tests on the anisotropy of rocks. The fixture can also be used in normal press machines to conduct conventional direct shear tests. The design and application of the fixture extends the function of large and sophisticated instruments to fully utilize experimental resources, and serves as an effective tool to study deep rock mechanics. Meanwhile, applying the new fixture in experiment teaching enriches experiment projects, which is in line with practical educational reforms in university. It also nurtures the students’ creative thinking and their ability to solve practical problems, which further facilitates the development of innovative experiment design.