Considering the uncertain factors as modeling errors and external disturbances existed in nonlinear systems,a Nonlinear Dynamic Inversion (NDI) control method was proposed based on Sliding Mode Disturbance Observer (SMDO) on-line compensation.The SMDO was designed for estimating the uncertain factors,and the output of it was used to design a new compensating control law,which was used together with NDI control for eliminating the influence of the uncertain factors.The simulation experiment based on Herbst maneuver is given to show the difference between the simplex NDI control and the proposed method.The simulation results show the effectiveness and robustness of the proposed method.