Abstract: The high temperature and pressure conditions of printed circuit heat exchanger(PCHE) in supercritical carbon dioxide power cycle may lead to core material failure and structure destruction, so it is necessary to analyze the stresses in PCHEs to optimize channel structures, and thus ensure the long-term safe and stable operation of the system. In this paper, the thermal, mechanical and total stresses of the specific paths of the hot and cold channels of the printed circuit heat exchanger core were analyzed by the finite element method. The thermal stress was compared in the range of 487.6~ 537.1℃. The effect of the tip radius of the semi-circular channel on the stress change was analyzed. The results indicate that the stresses are the combined effect of the pressure loading and temperature gradient and the total stress of the cold channel is greater than that of the hot channel; the stress concentration occurs owing to the sharp tips of semi-circular channels of the core, and the large temperature gradient in the middle of the semi-circular leads to the large thermal stress. Increasing rounded tip radius of the core can reduce thermal and mechanical stresses effectively in stress concentration regions, and the mechanical stress decreases more dramatically. Finally, it is pointed out that the stress concentration at the sharp tips should be relieved, and the etching depth should be controlled when the channel structures are designed. With the same hydraulic diameter, the maximum thermal stress, mechanical stress and total stress can be significantly reduced when circular cross section channels are adopted.