Background Heat pipe cooled reactors (HPR) have good inherent safety. In the early stage of core design, heat pipe failure accident is usually one of the design basis accidents that need to be considered. Purpose This study aims to analyze the neutronic-thermalhydraulic coupling performance of a new type of megawatt heat pipe reactor. Methods Firstly the heat pipe cooled reactor system physical models, including the point kinetics model, the core and heat pipe model and radiation heat transfer model for the inner core cavity, were established according to the designed HPR prototype composed of heat pipe stack and supercritical CO₂ Brayton cycle system with thermal power of 3.5 MW. Then, the finite element software FLUENT was employed to conduct neutronic-thermalhydraulic coupling calculation for the three-dimensional reactor core under the steady-state and heat pipe failure accidents. Finally, the core safety performance was evaluated by comparing the peak temperature of each component with the melting point of material. Results & Conclusions The results show the designed HPR has good safety performance under the steady state and single heat pipe failure. Radiation heat transfer in the core cavity cannot be ignored in the serious cascade three heat pipe failure accident in high power region. Meanwhile, the design cannot withstand cascading four heat pipe failure. By comparing the peak temperature of the multiple heat pipe failure with the peak temperature of the single heat pipe failure, it shows that the design has good inherent safety.