In the paper, a polyethylene terephthalate (PET) bottle tamperevident band broken detection algorithm based on contour curvature and corner detectionis proposed to solve the problem that no existing algorithm concentrates on PET bottle tamperevident band breakage detection.Firstly, the bottle cap area is roughly located by grayscale projection and the rectangular area ofthe cap is set to region of interest(ROI). Then, the cap edge point is obtained by gradient maxima suppression method,the subpixel edge is fitaccording to the given law isosceles triangle, and the bottle cap contour is connectedthrough the nearest point search method.And then,the stretch to distance ratio(SDR) of edge point is used to approximate the contour curvature,the corner points are detectedbased on maximum contour curvature, and the support ringis locatedby corner matching method. Finally, whether the tamperevident band broken is determined according to whether or nota gap exist between supporting ring and the tamperevident band.The algorithm detection correct rate is 94.75%,it meetsproduction needs.