Abstract: The paper calculates the transfer function of accumulators for thyristor rectifying charger based on microcomputer in detail and approximately settles the transfer function. It analyzes the characteristics of charger system and gives the designing methods of digital controller of charger system. It also advances the defining methods of magnifying coefficient of thyristor rectifying device in the microcomputer control system. At the same time, the main components, basic working principle and main functions of charger based on microcomputer are introduced.