Based on differential geometry theory, applying the dynamic extension approach of relative degree, the path tracking controller of mobile robot is designed by the input/output feedback linearization. And on the foundation, the exact feedback linearization on the kinematic model of mobile robot is realized. Its proof is different from and simpler than the literature (Robotics Comput Integ Manuf 16 (2000) 353). A practical point stabilization controller is proposed, and a fault in the literature (Robotics Comput Integ Manuf 16 (2000) 353) is indicated. Hence, the path tracking and point stabilization problems are solved in a unified approach. The designed controllers have the local asymptotic stability. Simulation results show their effectiveness.