Abstract: The solid core of the heat pipe cooled reactor（HPR）makes the thermal expansion effect significant. The coupling characteristics of the heat transfer and structural mechanical behavior are different between the HPR and traditional reactor cores. In order to optimize and evaluate the core design of the silent marine heat pipe cooled reactor called NUclear Silence ThermoElectric Reactor（NUSTER）,a fully thermal-mechanical coupling was used to conduct thermal-stress and safety analysis on the hot channel with highest power density,chosen from the NUSTER core design,using finite element software ABAQUS. It can be found that the air gap between the core components has a great influence on the temperature and stress distribution. Large safety margin is left for the thermal-mechanical parameters of the NUSTER reactor core,compared to the HPR reactor core safety limits proposed in this paper.