Abstract: The transformer no-load closing inrush current may cause safety problems in power grid, and the controlled switching technology with fixed target angle still has room for improvement in suppressing inrush current. A transformer inrush current suppression method and controlled-switching strategy are thus proposed based on changeable closing angle. The high voltage side PT or low voltage side PT of transformer is used to calculate the residual flux, and the target closing angle is adjusted according to residual flux. The key factors influencing the residual flux are determined, and the principles for choosing the target closing angle are proposed. A device prototype is developed and its effectiveness is verified through dynamic simulation and test station, which can provide reference for its engineering application.