Abstract: The technology of arcless on-load automatic capacity regulating for distribution transformer was dissertated, and technology scheme of arcless on-load automatic capacity regulating with power electronic switches was put forward. In this scheme, a kind of high-power withstand voltage thyristor with anti-parallel connection was used as capacity regulating switch, which overcame the drawbacks of mechanical switch such as complicated structure, slow regulative rate and high failure rate. The key technology of arcless on-load automatic capacity regulating of distribution transformer was discussed. Simulation model of the scheme was established using PSCAD/EMTDC. Simulation study and analysis for the shift and transition of power electronic switches were carried through, and the feasibility of this scheme was validated primarily. The results can provide solutions for the capacity regulating seasonally in country grid and peak-valley capacity regulating in city grid.