GIS is an indispensable electrical equipment in power system, but the operation experience shows that the effectiveness of the current commonly used GIS partial discharge detection methods is obviously insufficient. Seeking a GIS defect detection method with high reliability has become a bottleneck problem affecting the long-term operation safety of GIS equipment. As a non-electrical measurement method, light measurement method has a good detection effect on discharge in the weak light environment inside GIS, and has a broad application prospect. In this paper, the photomultiplier tube is used to carry out the discharge experiment in the 110kVGIS model, and the detection effect, attenuation characteristics and anti-interference performance of the optical measurement method for five typical defects are studied respectively. The results show that the optical measurement method has the detection sensitivity which is not lost in the pulse current method and the ultra-high frequency method. It has obvious attenuation characteristics with the increase of distance, but does not affect the detection accuracy. The anti-electromagnetic interference ability is obviously stronger than the electrical detection method. The experimental results of this paper have certain engineering value and reference significance for the application of optical measurement method in GIS partial discharge detection.