[en] The HTR-10, which now is under construction, is the first high-temperature gas-cooled reactor developed in China. The primary loop boundary components of the HTR-10 are peculiarly arranged as the reactor pressure vessel stands side by side with the steam-generator pressure vessel, and a hot-gas duct vessel connects them. This arrangement can diminish the thermal loads on the pressure vessels but can cause some new problems under seismic conditions. The design features of the support system of the HTR-10 primary loop boundary components are introduced. The procedure of seismic analysis of the support system is emphasized. Based on equivalent-static and dynamic calculations, the safety features of the support system under seismic conditions are demonstrated