The invention discloses a generator rotor magnetic pole T tail groove crack automatic detection device, and aims to solve the disadvantages of inconvenient operation, high labor intensity, long detection period, and potential safety hazard in the circumstance of a high rotor in existing magnetic pole T tail groove crack detection. The automatic detection device includes a base, the base is connected to a guide wheel connecting plate and a driving wheel connecting plate, the upper ends of the guide wheel connecting plate and the driving wheel connecting plate are hinged together, the lower ends of the guide wheel connecting plate and the driving wheel connecting plate are connected by an abutting spring, the lower end of the guide wheel connecting plate and the lower end of the driving wheel connecting plate are respectively connected to a lower guide roller and a driving roller, a driving mechanism driving the driving roller to rotate is mounted on the base, a detection probe is mounted at the upper end of the base, the left side wall and the right side wall of the base are respectively connected to a cushioning spring, the outer ends of the cushioning springs are both equipped with a side guide roller, support springs are connected to positions close to the left side edge and right side edge on the front side and rear side of the base, and the outer ends of the support springs are both equipped with upper guide rollers.