The helium circulator is a key component of the 10MW high temperature gas. cooled reactor (HTR-10). which assures the thermal energy transfer from the reactor core to the steam generator and operates at 3.0MPa. 250C helium condition. At the rated condition, the mass flow rate iS 4.32 kg S-1 and the pressure rise can reach 51.7kPa at the rotational speed of 5000 rpm. In fact, the pressure rise required for the HTR-10 is only 14.7kPa with a rotational speed of 3052 rpm. Thus, the layout of the blower contains a considerable margin. This paper presents the design procedures of the circulator during its development. Test results both in the factory and in the HTR-10 are given. Furthermore, the circulator design features and aerodynamic performance are highlighted.