Abstract: Supercritical carbon dioxide (sCO₂) is a kind of fluid with characteristics of appropriate critical point parameters, easy compression in the pseudo-critical area, abundant reserves to access, non-toxicity, and stable chemical structure etc. The Brayton cycle system using sCO₂ as the working fluid has advantages of simple structure, large compactness and high effectiveness at the medium or high design temperature. It has been drawn great concern in USA, France, Japan and Korea which are advanced in nuclear technology. Aiming at this technology, the micro-channel diffusion bonding (MCD) heat exchanger, a compact heat exchanger utilizing precision flow channel forming and diffusion bonding technologies, demonstrates exceptional temperature resistance and pressure resistance, heat transfer efficiency, and structural compactness. Its fundamental heat transfer unit employs diverse micro-channel configurations, among which the zigzag micro-channel exhibits superior heat exchange performance, structural simplicity, and mature manufacturability. To understand the influence of different parameters on the convective heat transfer characteristics of the working fluid and guide the performance optimization of zigzag micro-channel, the convective heat transfer characteristics of sCO₂ in zigzag micro-channel with bend angles of 15° and 30° were investigated through three-dimensional numerical simulations based on CFD method. Numerical study for pressure drops and heat transfer characteristics of sCO₂ flowing in the zigzag micro-channel were investigated in the dissertation. Heat transfer conditions were simulated. The results show that the ability of local heat transfer is related to the thermal and physical parameters of sCO₂. Large specific heat or high mass flux enhances the heat transfer ability. There is higher heat transfer coefficient (HTC) with lower system pressure near the pseudo-critical area, but the heat transfer coefficient is enlarged by higher system pressure in the gas-like zone because of low density. When the near-wall temperature enters the pseudo-critical region, the specific heat reaches an extremum, resulting in a 26.3% increase in heat transfer coefficient. Higher mass flow rates enhance turbulent pulsation intensity, strengthening heat flux at least by 21.7%. It’s found that the turbulent kinetic energy of sCO₂ will fluctuate continuously and periodically when it flows in zigzag micro-channel. Higher bending angle enlarges the amplitude of fluctuation, which enhances the ability of heat transfer finally. Moreover, it’s concluded that the capacity of turbulent kinetic energy is much higher in the corner of semi-circle cross section. Quantitative analysis of turbulent kinetic energy demonstrates that larger deflection angles (15° to 30°) produce higher oscillation amplitudes (averaged values increased by 38.9%), with local turbulent kinetic energy peaking at the bend sections due to secondary flow effects. This study provides theoretical guidance for optimizing deflection angle design in MCD heat exchangers operating under supercritical conditions.