The self-excitation power supply is a self-power supply technology for electronic transformers at high voltage side. In this article, the design principles and configuration methods are introduced of adopting complete self-excitation power supply in high-voltage substation. A technical improvement process and actual operation effect are illustrated of 110 kV substation in Mianyang. It is shown that the application of complete self-excitation power supply transformers simplifies system structure, exempts from periodic maintenance requirements for power supply equipment, improves the stability of the operation. The expected service life increases from 1~3 years to 15~20 years. Therefore, it is worthwhile popularizing the power supply technology to a large scale.