In order to obtain the dynamic charact eristics of micro-electro-mechan ical systems (MEMS),a MEMS in-plane motion measurement system to observe and a n alysis harmonic motions of microstructure is proposed in this paper.We present a implementation of phase-shift stroboscopic imaging system that can capture im a ges of high speed motions with a conventional camera,such as charge-coupled de v ice (CCD) camera.To achieve stroboscopic imaging,two external clock synchroniz ation pulses for external triggering of the camera and strobe light are generate d by FPGA,the triggering of the camera depends on how many times the LED light source flashes to make the camera produce a clear picture.After performing Cann y edge detection on the collected in-plane motion image sequence,the Shi-Toma si corner and Lucas-Kanade optical flow tracking method are used to perform motio n analysis to obtain the relevant motion information parameters of the device.Th e experimental measurement of a customized micro gyroscope using this system sho ws the measurement technology can achieve sub-pixel precision measurement of ME M S in-plane motion.Compared with the traditional LK optical flow method,it can reduce the measurement error caused by the change of the gray value of the image .This method has good measurement accuracy and the measurement repeatability ca n reach 10nm.