In this paper, a structurally optimized microchannel two-phase heat exchanger with a large number of submicron nucleation sites was proposed, and the subcooled flow boiling characteristic of a non-azeotropic immiscible mixture of HFE-7100 and HFE-7100/water was compared at flow rates of 50∼150 L/h and heat fluxes of 50∼400 W/cm². The results showed that the mixture of HFE-7100/water had higher boiling heat transfer efficiency in porous microchannels, lower heat exchanger junction temperature, and less wall superheat required for boiling compared to HFE-7100. In addition, the volume ratio of the binary mixture components had a significant effect on the twophase heat transfer characteristics, and different operating conditions corresponded to an optimal volume ratio based on the principle of thermal resistance-pumping power minimization.