Abstract: A total scheme of new auto-switching equipment for economic operation of power transformer is presented in this paper.Its hardware design，operation principle and the method of short-term load forecast method of periodical auto-regression model are introduced.Short-term load forecasting method is adopted to solve the problem of frequent input and retreat of transformer under the load undulation when implementing the economic operation control.Flexible auto-switching of transformer economic operation is realized by using programmable logic technology，it also satisfies the requirement of standby power supply auto-switching.Practical operation shows the given arithmetic and developed device in this paper achieve forecast aim and obtain good applicative effectiveness.