In these paper, a compliance control strategy based on force control for quadruped trot gait locomotion over unperceived rough terrain. To avoid interference of environmental disturbance and unknown model characters, a sliding mode based controller is designed to control the position/posture of the robot torso. The force distribution and control modules calculate desired contact force by eliminating interaction force between the stance legs. Simulations and experimental results demonstrate the effectiveness of our compliance control strategy as the quadruped robot successfully trotting over rough terrain.