In the skid steer vehicle the velocity constraints are quite different from other vehicle in terms of its wheels having to skid laterally to follow the curved path. The wheels of the skid steer vehicle are non-steerable; the vehicle is turned as the differential torque is applied to the wheels on the opposite sides. Motion control for skid steer vehicle is particularly challenging due to the non-linearities that arise from tire slip and braking. Moreover the instantaneous center of rotation may move out of the skid steer vehicle base causing loss of motion stability. Therefore it is difficult to model the accurate path following of skid steer vehicle. This implies that the control at the kinematic level is not sufficient enough and in general demands to use the dynamic model. In this research the mathematical model of four wheel skid steer vehicle is built with parameters of P-3AT skid steer mobile robot. This model is hybrid of vehicle dynamics and the semi-empirical tire model (TM-easy tire model). The model is used to synthesize and design of the sliding mode control law with fuzzy switching regulator.