The embodiment of the invention provides a method of detecting positional drop of a vehicle body characteristic line. The method includes the steps: making a section line perpendicular to the characteristic line at the matching position of the characteristic line; determining a starting point and an ending point of the characteristic line on the section line; according to the starting point and the ending point, determining comparison reference points on the section line; and based on the comparison reference points, determining the positional drop of the characteristic line. The method of detecting positional drop of a vehicle body characteristic line can determine the comparison reference points in a unified way, puts each comparison reference point in the same reference coordinate system, and can obtain quantized positional drop data, thus being convenient for evaluation and correction.