Abstract: The linear trajectory is one of major performance of industrial robots. This paper describes a vision-based non-contact measurement system capable of determining the linear trajectory performance of industrial robot. This system consists of active vision sensor, special measurement orbit, computer and correlative software. The vision sensor can be mounted on the end effector of robot arm, and the pose between sensor frame and measurement orbit frame can be determined by this system when the robot moves along the measurement orbit. So the system, much cheap and practical, can measure the straightness and repeatability of the robot movement trajectory. This paper will review the measurement devices of industrial robots at first, then describe the principle of our system, and discuss two key techniques mainly, including the 3-D coordinate calculation and image processing. At last the system the configuration and measurement result will be given.