Abstract: Optimization of the design of the general structure and flow path was carried out for the main heat exchanger of Low Temperature Nuclear Heating Reactor. The comparison of the schemes with and without optimization is described in detail. The structural stress and the external pressure buckling are analyzed in each working condition. The research shows that the main heat exchanger of the low-temperature nuclear heating reactor is with the advantages of simple structure, high economical performance, and easy of  in-service inspection and manufacture, and thus is worth promoting and applying in such reactors.