The thyristor valve is used as the core component in Static Var Compensator , according to the relevant IEC standards and the standards of the power industry regulation and the need of the project, in the factory must be high in a series of insulation test, to verify the withstand voltage and partial discharge start voltage whether meet the requirements. Due to the diversity of thyristor valve structure and insulation materials, resulting in the specified test voltage thyristor valve PD value exceeds the permissible value of the problems often occur, especially the thyristor 35kV class pipe valve, due to the high voltage rating, internal insulation weak parts are easy to produce partial discharge phenomena, have certain influence to the test, if not get effective treatment, the use of products running will bring severe hidden trouble of insulation. In view of the above question, through summarizing partial discharge in the high voltage test for a new thyristor valve of 35kV SVC(TSC) device , the theoretical analysis of the reasons for the problem, put forward the corresponding solution.