A brief introduction about the hydraulic control system of dry DCT was made, its principle and main characteristic were analyzed. A deep research on structure and principle of the piston displacement control system of dry DCT was made and model was built with EASY5. According to the model, the working characteristics were studied. Finally, by experiment, a further research of the piston displacement control system was made to verify the accuracy of the simulation model, which was the basis of the design of electrohydraulic control system and the development of the control strategies.