Insulator is the insulation equipment that is widely used in power system,and the discharge will occur on the insulator’s surface if the insulation performance decrease to certain degree, to detect the discharge optical radiation signal can be used to characterize the equipment insulation condition. Usually, the surface discharge is the corona weak discharge, so the optical signal mainly distributes below 400nm UV band. To detect the solar band UV signal, it not only can help us to find the early discharge, but also we can detect the discharge in the daytime. In this paper, a discharge ultraviolet signal detection system was designed with a solar blind ultraviolet PMT sensor, first, the detection principle is introduced, then the hardware and software key parts are introduced in detail, the hardware realized the function of optical signal to current signal conversion, signal processing and data acquisition, the software was developed with virtual instrument, it can realize the signal acquisition card control and analysis. Testing showed that this system has the characters of good linearity and high-sensitivity, but test also showed that the outside sun light had certain interference effect. Finally, the insulator surface discharge was test with this system, studies show that the system can effectively detect the insulator surface discharge.