An adaptive digital sliding mode control position controller was designed for a numerical control (NC) machine planar motor servo system with friction, parameter, and external disturbances. Firstly, the model of the NC machine planar motor servo system is discretised digitally. Secondly, the model parameters are identified using a recursive damping least squares method. Then, an adaptive digital sliding mode position controller is designed according to the state-space equation of the digitally discretised NC machine planar motor system, and the stability of the designed control system is analysed using Lyapunov’s theory. Finally, the effectiveness and superiority of the designed control method are verified by simulation experiments.