This paper describes a design of the gas-turbine system in a 400MWt HTGR closed cycle helium gas turbine power plant. Design of turbine, compressors, generator and FP filter are given. Results show that; (1) Compactness and enlightening of turbine and compressors are achieved in these designs with high performance, (2) Helium cooled generator combined with static starter system is adapted in these design, (3) FP filter of high removability against ^<110m>Ag and graphite particle in high temperature helium coolant was designed by sintered filter material made of Hastelloy X.
