Abstract: Heat pipe reactor has the advantages of long life and high reliability, which is one of the research focuses of space nuclear reactor.In order to study neutronics and thermal-hydraulics coupling phenomenon in the transient process, based on the semi-physical simulation technology, experiment platform of neutronics and thermal-hydraulics coupling was set up in view of the heat pipe reactor core scaled model. The temperature distribution of the core scaled model was measured by the experiment module, and the output power was calculated by the simulation module. The transient response characteristics of core scaled model was explored through the experiment module and the simulation module. The transient change process of temperature, power and excess reactivity with the different initial reactivity insertions was studied, which revealed the temperature hysteresis characteristics of system due to the capability of heat capacity, namely the phenomenon of thermal inertia. The results show that the thermal inertia of the core scaled model decreases with the increase of the initial reactivity and the initial power level and is inversely proportional to the thermal diffusivity of the substrate.