Abstract: The line-type pulse modulator is used as the pulse power supply in electron linear accelerator. Compared with the traditional pulse forming net (PFN) charging technique, LC series resonant charging technique, which represents one of the development directions of high power line-type pulse modulator, has the advantages of higher efficiency and smaller size. The work principle of LC series resonant charging technique was introduced and a prototype was developed in the paper. Based on engineering applications and experiment results, the method to improve stability was proposed. The experiment results show that the designed method and the power supply meet the requirement of design specifications.