Abstract: The purpose of piping analysis is to demonstrate the safety of piping, equipments, supports and other attachments. Three items are included in the analysis, which is calculating the stress to measure up the security of piping system according to RCC-M; calculating the counterforce of piping on the supports which are used for support design; calculating the counterforce of piping on the equipments and other attachments to ensure safety in the operating. The process of piping stress analysis is performed as below. Firstly, making clear the calculate scope; secondly, building the mathematical model and inputing the material characteristics; thirdly, inputing loads and combining them in differente ways under different conditions; finally, calculating the stresses and comparing them with allowable value of RCC-M. Piping stress analysis is not only important to protect pipeing system, equipments and supports, but also play an important role in optimizing the design of system, and the building and operating of nuclear power plant.