The key research of rock mechanics is static or dynamic behavior between rock materials with various shapes of contact surface. The basic approach of the contact surface mechanics property research is through the contact surface basic mechanics property test. To get steady shear strength of rock joints, shear strength of different size of samples need be tested. Hydraulic system and control scheme of a new device were introduced based on existent direct shear apparatus. At the same time, control accuracy and methods of normal force and shear force were analyzed. The accuracy was validated by several laboratory and in situ experiments. It meets engineering design demand. The research provides large pressure range and flexible control apparatus in testing stress dilation and size effect of sample.