Abstract: Considering characteristics of steel strips, an algorithm of surface defects initial inspecting for steel strip is designed to solve whether steel strip contains defects or not. It can meet requirements of automatic inspection. Using difference of physical characteristics of second moment invariant , the aim of recognition for the defects in steel strips is accomplished, it is proposed that changes of strip images containing defects are sharper than those containing no defect after image blocking and block scrambling, because moment invariants keep invariant after the image is transformed via translation, scaling, and rotation. The experimental results demonstrate that the algorithm can recognize steel strip images containing defects, making initial inspection and recognition parallel, and it is meaningful to improve efficiency of surface defect inspection system of steel strip.