Abstract: The support of reactor pressure vessel is the key part in the structural design of nuclear power plant. The wall at support position of reactor pressure vessel of Huaneng Shandong Shidaowan high temperature reactor demonstration project was taken as the research object. According to the theory of local pressure, combined with the concrete stress characteristics of the wall at support position of reactor pressure vessel, the multiaxial strength criterion of concrete was used to analyze the local concrete stress of the side frame,the lower frame and the bolt group in the composite stress state. According to the finite element elastic and elastic-plastic calculation results and the structural analysis, the shortcomings of the original design scheme were found and the optimization suggestions were put forward. According to the optimized design scheme, the bearing capacity and construction feasibility of the wall were analyzed and demonstrated again to ensure that the area met the requirements of the current national standards. Most of the research results in the paper were adopted by the demonstration project.