The invention discloses a supersonic flow field predicting accuracy determination device and method based on image processing. The method comprises the steps that 1, a supersonic flow field schlieren experiment map and a numerical simulation map are obtained; 2, the schlieren experiment map is adopted as a reference, the schlieren experiment map and the numerical simulation map are aligned; 3, flow field shock wave lines in the schlieren experiment map and the numerical simulation map are extracted respectively; 4, position coordinates of points forming the flow field shock wave lines in the schlieren experiment map and the numerical simulation map are extracted respectively, the curve fitting degree of the two flow field shock wave lines are calculated, and the similarity of the schlieren experiment map and the numerical simulation map is determined. According to the flow field image obtained through a schlieren experiment and a cloud atlas predicted by flow field simulation, firstly, images with fully-corresponding sizes and positions are obtained by matching characteristic points. Flow field characteristic lines needing to be researched are obtained through characteristic line extraction, and finally the flow field similarity of the schlieren experiment map and the numerical simulation map is obtained through curve fitting, so that flow field simulation predicting result accuracy determination is achieved by means of the flow field schlieren experiment result.