Abstract: The technical parameters of supercritical direct current steam generator used in Modular High Temperature Gas Cooled Reactor（MHTR）are presented in the paper. The helical tube structure design concept and structure size of transfer heat tube bundle were provided, and the heat transfer characteristics of tube bundle at supercritical pressure were analysed. After thermal-hydraulic analysis and calculation, the design is proved to meet the thermal and hydraulic requirements and not occur the heat transfer deterioration at the design condition.