Abstract: In recent years, the integrated modular reactors have developed rapidly, and China is also accelerating the development of integrated modular reactors. In this paper, a helically coiled tube steam generator was designed for a 15 MW Integrated Modular Reactor. 12 assemblies were distributed in the annular space between the reactor core and the pressure vessel. There are 5 layers with 25 helically coiled tubes in each assembly, with a total of 300 helically coiled tubes in the steam generator. The parameters of the steam generator assembly are given. The heat transfer coefficient, temperature, temperature difference, and heat flux along the tubes were analyzed. Pressure drop with the flow rate characteristic curve of the fluid in the helically coiled tubes is also shown.