Inspired by the leaf vein structure, this article proposes cooling structures with tapered contracting manifold and leaf vein feature, to optimize the cold plate structure for high heat flux gallium nitride high electron mobility transistors (GaN HEMTs). The correlation between the fluid flow distribution in channels and the temperature uniformity of chips is investigated. The performance of the designed Bionic Structures is compared with that of the traditional Parallel Structure in terms of fluid flow characteristics, heat transfer characteristics and comprehensive performance. Results show that the Bionic Structures with tapered contracting manifold and leaf vein feature improve the fluid flow uniformity by up to 44.1 % and the temperature uniformity of chips by up to 65.0 %, while reducing the pressure drop by up to 24.7 % and the convective heat transfer resistance by up to 32.8 %. The comprehensive performance is also significantly improved. This article demonstrates the great potential of bionic cooling structure for breaking through the thermal management limit of high heat flux power chips.