Abstract: In order to satisfy the requirement of the lower hybrid current driven(LHCD) system on HL-2A, the high voltage power supply based on pulse step modulator is designed and analyzed. Many modules are connected in series, and the output voltage can be adjusted continuously. The power supply with low voltage and low frequency can be transferred into the power supply with high voltage and high frequency. The power and stability and redundancy are increased. The parameter and type of the components in the module including their technology layout are analyzed carefully. The leakage inductance of the multi-winding transformer is used as the filter inductor. The metallized film capacitors and the IGBT are adopted. The high voltage transformers with 29 second-windings are designed. The control algorithm and control system are designed to satisfy the requirement of the load. Test results especially the over-current protective test results are shown. The practicabilities of the two main control algorithms are tested. Many parameters especially those for quick protection and stability of the power supply can satisfy the requirement of the load.