A portable on-line infrared, ultrasonic and ultraviolet synthetic partial discharge measurement system is realized by using image registration and fusion technologies. Firstly, the measurement principles and modular structures of infrared, ultrasonic and ultraviolet technologies are presented respectively. Then, a computer is used to fuse the three kinds of partial discharge measurement signals. The fused signals are put into the equipment image acquired by a camera. Thus, their corresponding relations with the equipment image are established. The proposed system not only can display the location imaging videos of infrared, ultrasonic and ultraviolet signals respectively, but also can fuse the above three kinds of signals into one video interface, so as to display the partial discharge location and its variation in three measurement methods directly. The results show that the system has the advantages of portability and fast measurement. It can find the faults in power equipment in time. Therefore, it has wide applications.