Aiming at the demand of aeroengine thermal management system, this paper proposes a regular octahedral porous structure heat exchanger and studies its internal flow and heat transfer characteristics. The study find that the regular octahedral porous structure can effectively improve the heat exchanger efficiency, but with the decrease of C_e, the flow resistance outside the pipe will increase rapidly. When the C_e decreases to 10, the coefficient of resistance outside the tube increases to 18.2 times as much as that of the light pipe. Therefore, the internal structure optimization of the heat exchanger is carried out. In the case of improving the internal heat transfer, the internal flow resistance is reduced as much as possible, thus obtaining the optimal heat transfer resistance comprehensive coefficient C_e.