Abstract: Based on PD 6493, R/H/R6-95 and SAPV-99, fracture failure risk analysis method is developed for assessing in-service pressure piping containing various defects, considering the uncertainties of several main random variables, such as defect sizes, suffered loads, material fracture toughness. Applying Microsoft Visual C++6.0, the safety assessment system of in-service pressure piping containing flaws (SAPP-2002) is successfully developed. The safety probability of separate defect and the failure probability of the whole pressure piping can be obtained by this software. The regions needed to maintain at present can be deter-mined by risk analysis results. Additionally, based on structure analysis module of in-service pressure piping of SAPP-2002, the most dangerous positions or the highest risk regions in the piping can be known, which can be used as a guideline to make some suggestive reconstruction schemes or maintenance measures. Then, the safety condition of in-service pressure piping can be improved to prevent the underlying accidents and the failure probability of the whole piping can be also reduced.