The invention discloses a transformer voltage regulating switch shift validity check method. The method comprises the following steps: step S01, acquiring high-voltage side voltage UH and low-voltage side voltage UL of a transformer and a voltage regulating switch shift D in real time, and then turning to step S02; step S02, determining whether a shift change exists, and in case of the shift change, turning to step S03; S03, according to the low-voltage side voltage UL and the voltage regulating switch shift D, calculating a high-voltage side voltage theoretical value U'H, and then turning to step S04; and Step S04, according to the calculated high-voltage side voltage theoretical value U'H, the acquired high-voltage side voltage UH of the transformer and a voltage regulating step length k, determining which is larger between |U'H-UH|/UH and the k, when the |U'H-UH|/UH is smaller than the k, it indicating that a checked shift is correct, and otherwise, it indicating that the checked shift is wrong. The method provided by the invention can improve the shift acquisition reliability of the transformer and prevent misoperation of transformer differential protection due to a shift error.