Abstract: Taking the faulty intermediate joint of a 35 kV cable made by melting technology as the research object, the failure causes were analyzed by physical object disintegration and cable performance testing, and the same processing technology was adopted to make the cable intermediate joint again with the same voltage grade.After eliminating the influence of the existing problems of melting technology itself, it is considered that the main reasons of the fault are improper treatment of key technology caused by fatigue construction, and excessive local field strength caused by impurities on the surface of wire core, which lead to breakdown discharge at the intermediate joint of the cable.