This paper describes the basic principle of step controlled high-voltage shunt reactor，analyzes the influence on each control branch when short-circuit fault occurs，and concludes that the current of the control branches on the short circuit point and lower short circuit point decreases significantly.So，a protection scheme is proposed as follows:first，the real-time current of all auxiliary reactors is calculated，then the constant value setting methods of different auxiliary reactors and different capacities are analyzed based on the theoretical current value of auxiliary reactors，the two should be compared to become the current criterion for distinguishing fault and its location.Real-time digital simulator（RTDS）experiment results show the protection scheme has the following features:quick judgment，accurate positioning，sensitive current criterion，wide scope of coverage and easy setting of constant value.