For the problem of pressure vessel weld defect detection, this paper use VC++ and MATLAB mixed programming method for defect detection. This paper mainly describes the steps and advantages of VC++ and MATLAB mixed programming that use of MCC compiler in MATLAB and used for the pressure vessel welds image processing and quality assessment software development. Users can get an intuitive processing and evaluation results through just a simple menu operation. This method was superior to the effects of separate using VC programming and give full play to the VC++ and MATLAB respective advantages. The results show that, VC and MATLAB mixed programming can reduce the programming effort and improve software development efficiency.