A high precision wire diameter measurement simulation system is designed, which is composed of parallel light source, double telecentric lens, CCD camera and object to be tested. Considering that this experimental system is designed to simulate the photography and measurement of high-speed wire, the radial velocity of wire rod can be as high as 100 m/s in the rolling process, and there are signs of transverse runout. Therefore, in the optical design, a telecentric lens with a fixed magnification rate is used to keep the image size on photosensitive surface unchanged when the distance is changed. Moreover, the maximum exposure time of the selected plane array CCD can reach 1μs, thus a high-definition image reflecting the size of the measured object can be obtained in real-time. The experimental results show that the diameter accuracy of the workpiece measured by the simulation system can reach 20 μm, which can meet the needs of production.