In order to ensure the reliability of valve for nuclear power system, according to the real dimension of the safty relief valve body, the modeling for three-dimensional steady thermal-structure coupling is established considering the heat exchange between valve body and internal medium, at the same time between valve body and environment. By using the multiphysics field of the ANSYS software, the thermal-structure coupling effect of valve body is simulated with the appropriate gridding density. On this basis, by using the probabilistic design system of the ANSYS software, the structure reliability analysis of valve body is simulated, based on Monte-Carlo simulation method. The results show that the structure reliability of the valve body is enough under working circumstance. Sensitivity of the random variables on maxstress is also researched, and it is obtained that L is the most significant variable on reliability. But the design for thickness of the valve body seems to be too conservative, on the premise of ensuring reliability, the body structure can be improved by decreasing parameter L, saving material up to 52.7％and peomoting technology level of safty valve effectively.
