Abstract: Applying supercritical evaporator to nuclear power can greatly improve the thermal efficiency of the unit. Due to the significant variations of fluid properties in the pseudo-critical region, it is important to study the flow and heat transfer characteristics of supercritical pressure fluid in helical tubes, which helps to design the supercritical helical tube evaporator. The heat transfers of CO₂ at supercritical pressures in a helical tube under constant heat flux conditions were numerically investigated in the present study. Both RNG k-ε turbulence model and SST k-ω turbulence model were applied in the simulations, and the numerical calculation results show that the SST k-ω turbulence model agrees better with the experimental data. Effects of mass flow and heat flux on wall temperature and heat transfer coefficient were analyzed based on this model. It is found that with the decrease of mass flow or the increase of heat flux, the peak of heat transfer coefficient is further away from h_pc. Circumferential wall temperature and heat transfer coefficient distributions at different cross sections along the flow direction were also studied. The results show that the highest wall temperature occurs at φ of 315°, which should be gained extensive attention of operation in order to ensure the safe operation of helical tube evaporator.