Abstract <p>The length of the irregular head and tail regions of medium and thick plates is a crucial factor affecting steel yield. This paper proposes a shearing length calculation method based on multi-modal edge feature fusion to address the limitations of current detection methods in shape recognition and length calculation accuracy. First, high-resolution industrial cameras capture the surface images of the steel plate, and motion distortion errors are corrected to accurately obtain the outer edge profile. Then, a dual-objective optimization model is designed, integrating width consistency criteria and edge linearity constraints, ensuring precise adaptive positioning of the shearing position. Finally, the shearing length of the irregular head and tail regions is calculated using the constructed cutting guide lines, and a polynomial regression error correction model is applied to improve calculation accuracy and stability, yielding the effective plate length. Experimental results show that the maximum error in detecting the shearing length of the head and tail is less than 1mm, with a 0.4% increase in steel utilization. The method has engineering application value by adjusting and optimizing rolling process parameters based on the shape and length of the irregular regions.</p>