Abstract: The paper describes the essense process for building the metal system for filling D T gas under the high pressure. The system's leakage under the pressure of 15 MPa is ( 3.7～ 4.8 )×10 -4 Pa·L/s. The system is very safe and reliable proved by the experiment of filling gas to the microsphere, with handing a large quantity of tritium, e.g., 2.8×10 14 Bq.