Abstract: In this paper a non-time based approach is proposed for a mobile robot to track paths. Firstly the x-axis projection of the mobile robot's actual path in some reference frame is selected as the non-time reference based on which for a kind of geometric paths the kinematics model of the mobile robot is built and the corresponding tracking control law with constant velocity is designed, then the strategy of tracking any geometric path is presented. Since the tracking system is based on the non-time reference and is immune to the time factor, its tracking capability in the uncertain environment can be improved. Simulation and experiment results are given to demonstrate the effectiveness of proposed method.