As the measuring accuracy of traditional robot visual measurement system is limited by the robot absolute positioning accuracy, a new high-precision robot vision measurement system based on the workspace Measurement and Positioning System was developed and its calibration technology was researched. In this system, the robot end-effector can be positioned precisely by the workspace Measurement and Positioning System in real time, freeing its positioning accuracy from the robot accuracy. The system only makes use of the high flexibility and automation of the robot. In order to realize the high-precision measurement, a new calibration method of calibrating the exterior parameters of the visual sensor based on the homography matrix was proposed. In this method, a calibration target was designed and imaged by the visual sensor. With the aid of laser tracker for coordinate transformation, the external parameters can be easily determined with only one image of the calibration target. The verified experiment shows that the distance measuring accuracy over the robot working volume is superior to 0.2/mm, which has been improved significantly compared with the traditional robot visual system.