The correctness of the transformer CT wiring is the basis for the correct operation of the transformer protection device and the accurate operation of the measurement and control device. In order to solve the problems of poor accuracy, complicated procedures, and low efficiency of the current main transformer CT secondary circuit wiring verification scheme, a method based on the instantaneous reactive power theory utilizing the inrush current during the transformer no-load closing period to verify the high-voltage side CT wiring is proposed. By analyzing the inrush current’s mechanism and using its power characteristics, this method can verify the CT polarity and phase sequence wiring on the high voltage side of the transformer. Once wiring errors are detected, the protection device will act after the delay setting. While effectively improving the startup efficiency of new transformer equipment, the reliability of system operation is improved. RTDS simulation and experiment validate the effectiveness of the method. This work is supported by Science and Technology Project of Yunan Electric Power Company of China Southern Power Grid (No. YNKJXM00000511).