Abstract: Through the rationally simplifying helically coiled tube steam generator of the system integrated modular advanced reactor (SMART), the single-tube model of helically coiled tube steam generator was established. Based on two fluids model and non equilibrium subcooled boiling model, the flow and heat transfer process in the helically coiled tube under different parameters for the steam generator was numerically simulated with constant heat flux. The results show that the numerical results of friction pressure drop are the closest to Chen Xuejun’s correlation. When the curvature decreases from 0.04 to 0.012, the friction pressure drop decreases significantly, but the friction pressure drop does not change as the curvature below 0.012. The acceleration pressure drop is almost unaffected by curvature. The calculated friction pressure drop is not affected when the angle varies from 3° to 8.6°. The total pressure drop and the friction pressure drop increase with Reynolds number, while the friction pressure drop gradient increases obviously.