This paper presents a noval robot teaching system based on Augmented Reality to solve several problems like the inefficiency in off-line programming, low interactivity, etc. Combining a motion capture system and a mixed reality head-mounted display (Microsoft HoloLens) and a 6-DF robot arm, we design a robot teaching system with three main functions: 1) Trajectory programming, 2) visualization of trajectory information, 3)virtual previews of robot motion. Firstly, we make coordinates transformation among HoloLens, motion capture system and robot arm. Then, we superimpose the virtual robot arm on the real industry environment by using virtual reality technology. Additionally, we use the motion capture system to capture the data of three-dimensional position of handheld demonstrator and save these data to the register of the real robot arm for trajectory programming. Finally, we transfer those data to HoloLens to achieve visualization of trajectory information and the virtual preview of robot motion.