The honeycomb Ultra-compact Plate Heat Exchanger (UCPHE) with hexagonal channels is proposed to be the recuperator in the supercritical CO2 (SCO2) Brayton cycle. The flow and heat transfer characteristics of the SCO2 in the UCPHE are investigated numerically by means of SST k-omega turbulence model. The study shows that the buoyancy effect has weak effect on heat transfer due to the insignificant variation in the thermo-physical properties of the SCO2 under the high temperature condition. The turbulent kinetic energy and the intensity of secondary flow reach the maximal value near the pseudo-critical point due to the significant buoyancy effect, resulting in the heat transfer enhancement. The performance evaluation of the UCPHE via Nu/f(1/3) is implemented and its optimum geometry is proposed. The study concludes that the UCPHE has a better comprehensive performance than the Printed Circuit Heat Exchanger (PCHE) within the range of the Reynolds number from 3000 to 35,000.