Abstract: A sliding mode control(SMC) method was proposed and applied to a rigid body attitude tracking system in the presence of dynamic uncertainties.First,a model of the attitude tracking system was built in terms of the decomposed error quaternion,then feedback linearization was used to obtain the required angular acceleration.The SMC algorithm was proposed to make the angular acceleration of the rigid body track the required angular acceleration.Simulation results show that the proposed SMC law is globally stable and insensitive to the uncertainties and variations in its inertial parameters,and control actuator aligment and external disturbances.