Abstract: The reactor vessel is an important safeguard for nuclear safe, it must insure that the reactor vessel as a pressure vessel meets the requirements of the RCC-M code by stress analysis. First, 3D model of the reactor vessel is built with ANSYS which is a finite element analysis software. Then, the stress intensities of the reactor vessel effected by different pressure, temperature, earthquake and other loads were computed. Last, the result with limits applicable showed in RCC-M was compared. This report shows that the reactor vessel meets the requirements of the RCC-M code under calculated condition and shows a good way for primary equipments stress analysis.