The invention discloses a wheel tread abrasion detection method based on a laser displacement sensor. The method includes the following steps: arranging a 2D laser displacement sensor that is positioned lower than a steel rail plane position outside a track; sectioning data corresponding to wheels by analyzing distribution rules of the number of output effective value data points, and filtering wheel brake disc and vehicle bottom device data that is inconsistent with the wheel data; on the basis of mounting position parameter values of the laser displacement sensor, converting a coordinate system xoy of the sensor into a tread reference coordinate system uov through coordinate rotation; combining contour data of standard wheels and data measured by the sensor, and obtaining complete contour data of wheels; and selecting data about the smallest wheel rim as optimal tread data, and calculating wheel tread abrasion, wherein a difference between a standard wheel rim height and an actual wheel rim height is a tread abrasion value. The method is simple in measuring principle, provides a stable system, and can meet actual demands of tread abrasion measurement.