In the production process of hot rolling strip, wave-shaped defects appear at the edge of strip, which affects the quality of steel and the interests of steel enterprises. In this paper, the method of identifying and calculating the wave-shaped defects on the working side of strip steel based on the convex hull detection algorithm is discussed. Firstly, the classic Graham's Scan algorithm is used to detect the processed strip images. Then, the accuracy of the algorithm is discussed, and the error judgment of wave shape defects is analyzed. Finally, the improved Graham's Scan algorithm was used to detect the wave-shaped defects of strip steel again. The experimental results show that the improved algorithm can significantly reduce the misjudgment and has high utilization value in the actual production process. The actual problem is solved by processing the image.