A robust adaptive controller with guaranteed transient performance under a desired compensation adaptation law is developed for trajectory tracking control of robot manipulator in the presence of parametric uncertainties and external disturbances. With some modifications to the conventional adaptation law, a new control law is redesigned by combining the design methodologies of adaptive control and sliding mode control. The adaptive scheme has best computationally efficient for real-time calculating of the regressor, and compensate nonlinear friction and external disturbances via thought of variable structure. The global asymptotic stability is validated by Lyapunov direct method. Because the adaptation law is robust to uncertainty, the parameter is not contaminated with noise, simulation results show the estimated parameters are converged and the good robust and accuracy are obtained.