Abstract: A strategy of the admittance control based on virtual fixtures is proposed to solve the potential safety problem caused by the incorrect operation of the doctor and the complexity of the surgical space during the human-robot cooperative surgery. The tube virtual fixtures, the cone virtual fixtures and the forbidden-region virtual fixtures based on artificial potential field are designed according to the principle of admittance control and the features of drag-guided phase, precise positioning phase, surgical operation phase in human-robot cooperative surgery. And the simulation experiments of knee replacement surgery are carried out on the self-developed surgical robot. The results show that the tube virtual fixtures can effectively assist the robot move along the trajectory; The cone virtual fixtures can effectively reduce the positioning error of the doctor dragging the robot, and the positioning error is 0.23 mm; The forbidden-region virtual fixtures can effectively prevent the robot from crossing the operation area and ensure the safety of the surgical operation.