The invention discloses a mine elevator winch principal axis radial deflection detection method and a monitoring device. The monitoring device comprises a high-definition camera, an image processing module, a target monitoring module, a feature extraction module, a calculation module, a display and an alarm, wherein the lens of the high-definition camera is parallel to the end face of a brake disc and aligned with local edge of the end face of the brake disc; the high-definition camera, the image processing module, the target monitoring module, the feature extraction module and the calculation module are electrically connected in sequence; the display and the alarm are electrically connected with the calculation module respectively; through calculation, the maximum deflection and the deflection direction of the brake disc, namely, the radial deflection and the deflection direction of a winch principal axis, are obtained. According to the mine elevator winch principal axis radial deflection detection method and the monitoring device, the radial deflection of the winch principal axis can be monitored in real time; the radial deflection and the deflection direction of the winch principal axis are displayed through the display; the alarm is equipped to give an alarm when the deflection is up to a set threshold.