Digital control experiments are important parts of electrical engineering course in modern electrical schools. A virtual digital control experimental system is developed for undergraduates to learn digital control principals and to practice online. Based on the digital control hardware experiment platform, the practical circuit model is developed. And some digital control algorithms are employed for virtual digital control operations, these algorithms include PID and some varies algorithms, Smith predictor algorithm, Dahlin algorithm and Kalman algorithm. The development of the Kalman filtering algorithm in the virtual experimental system is detailed. The experimental parameters of the plant and the controller can be flexible configured by the users in the terminal online, and the control results can be quickly displayed online. The virtual digital control experimental system is efficient for undergraduates to pre-practice the digital control experiments and to learn the control principals.