Abstract: In order to control the snake robot to follow desired paths on the ground with unknown friction coefficients, a path following method is proposed based on the angle symmetry adjustment. According to the kinematics analysis, if the joint angle changes symmetrically, the locomotion direction of the robot doesn't change. Otherwise, the locomotion direction will change. Based on this idea, a parameter is set in the torque control, and it can adjust the angle symmetry which is regulated by the positions of the target point and the robot. The target point is set on the desired path, and it is constantly updated along the desired path as the robot is moving. When the robot does not move along the desired path, the direction parameter changes asymmetrically. Negative feedback control is used to decrease the degree of asymmetry until it vanishes, so that the robot moves along the desired path again. Finally simulations on different grounds with unknown friction coefficient are carried out, and the trajectories and the errors obtained show that the robot locomotion direction can be adjusted according to the desired path. The proposed method can not only control the snake robot to follow the desired straight and curve paths on different grounds with unknown friction coefficient, but also complete the path following task when side slip occurs.