Austenitic stainless steels(ASSs) are commonly used for nuclear piping due to high mechanical properties and corrosion resistance. Thermal embrittlement(TE) is one of the aging degradation mechanisms which can affect the loss of integrity of the ASS piping. Therefore, the effect of TE on the ASS piping should be considered when the flaw evaluation is performed. In this study, an integrity evaluation program for the ASS piping was developed based on ASME B&PV Code, Sec. XI. End-of-period flaw size was calculated by Appendix A and flaw evaluation was performed by Appendix C. Moreover, the increased tensile properties of the ASS piping under several thermal aging embrittlement conditions were considered. For verification and validation of the developed program, representative data of the ASS piping in an operating nuclear power plant were applied. The effect of TE was examined by comparing stress intensity factors obtained from each thermal aging condition. The developed program provides graphic user interface so that final evaluation results such as crack sizes under specific transient loading conditions can be confirmed visually.