Abstract: As a kind of passive equipment with high efficiency, reliability and long-distance heat transfer, heat pipe is widely used in the field of nuclear energy. The reactor with heat pipe as the main heat transfer component came into being, which is heat pipe reactor. The main difficulty in the research is the heat transfer of heat pipe. There are some heat transfer limits in the work of heat pipe, which hinder the heat transfer of heat pipe. At this stage, there are few studies on the heat transfer limit, and the occurrence law of many limits has not been mastered. The theoretical and experimental researches on the heat transfer limit mechanism of liquid metal high-temperature heat pipe are of great significance to improve the heat transfer performance of heat pipe. In this paper, the existing heat transfer limit of high-temperature heat pipe was briefly described, the experimental research was carried out on the heat transfer limit of capillary driven high-temperature heat pipe with working medium of sodium, and the experimental platform for heat transfer limit analysis and test of high-temperature heat pipe was designed and built. The heat transfer limit of capillary driven heat pipe with working medium of sodium and liquid filling of 158 g and 208 g was experimentally and theoretically studied. The horizontal inclination working condition was designed from 0° to 90° and the heating power was from 1 kW to 7 kW. In terms of experiment, an experimental platform for heat transfer limit test and analysis of high-temperature heat pipe was designed and built, and the changes of heat transfer power of liquid metal high-temperature heat pipe under different horizontal inclinations and different heating powers were studied. In theory, the correctness of the theoretical models of continuous flow limit and entrainment limit was verified, and the occurrence laws of the two limits were summarized. It is found that the occurrence of continuous flow limit of heat pipe affects the start-up stage of heat pipe. Because the transition temperature is higher when the horizontal included angle is large, the continuous flow limit is more likely to occur in the heat pipe at large angle. The prediction error of the empirical model is less than 6.58% at small angle and more than 28% at large angle. When the entrainment limit occurs, the temperature in the evaporation section of the heat pipe rises sharply and the temperature in the condensation section fluctuates. The greater the inclination angle of the heat pipe, the easier the entrainment limit occurs. The empirical model has errors at different angles, and the error at large angles exceeds 100%. This paper summarizes the occurrence laws of continuous flow limit and entrainment limit, which provides a reference for the design of heat pipe in advanced nuclear reactor system.