Abstract: As an efficient means for heat transfer, heat pipes have the characteristics of high reliability, low temperature difference and no need of external driving, so they have been widely studied and applied in aerospace, nuclear engineering and other fields. In order to apply this technology to the design and development of new type reactors, the theoretical method and performance analysis code of heat pipe were researched. The structure, working mechanism, type and performance characteristic of heat pipe were analyzed. The heat pipe theory and calculation models of heat transfer limits were studied. On this basis, the heat pipe performance analysis code HEPAC was developed, which had the ability to analyze the heat transfer characteristics and calculate the heat transfer limits for various types of heat pipes. The HEPAC code was tested and verified by comparing with the relevant experimental data. The code development provides an important tool for the design and analysis of various types of heat pipe reactors.