Abstract: In this paper, an automatic quantitative recognition software system for welding microstructure (WM SQRS) has been successfully developed under the integrated compiling environment of Microsoft C/C++7.0. On the basis of gray character and geometrical pattern features of welding microstructures, several key characteristic parameters have been creatively extracted, and the correspondent recognition function and a minimum-distance classifier have been constructed. Using this system, quantitative recognition and analysis of microstructures in welded joints made of the mild and the low-alloy steels can be done automatically. Its accuracy, reliability and reappearance can satisfy requirements of quantitative analysis of welding microstructures. The software has great theoretical and practical significance in setting up the quantitative relationship among the compositions, microstructures, and mechanical properties of welded joints, selecting appropriate welding materials and suitable processes, improving welding quality and developing quantitative welding metallurgy.