The paper introduces the -35 kV/200 kW high voltage power supply (HVPS) [1]which is specially used to test klystron units in LHCD [2] system. The new klystrons must be tested under high voltage level before operation and the old klystrons which have worked for a longtime must be exercised by HVPS in lower hybrid current drive (LHCD) system. As the former HVPS has some shortages in engineering design and operation design, the HVPS has to be modified and rebuilt by adopting new method and technology to solve existing bottle-neck problems.