Abstract: It deals with a new rare gases metal purification and mass spectrometer analysis line better than the glass line. The system static vaecum keeps at 10~(-7)torr for about 16 hours. It gets He, ve and Ar effective separation by a charcoal trap at a temperature of -195℃, so the line can be used to analyze Ne isotopes. Spike is sampled by our spike line system. The mass spectrometer has a resolution of about 105 at 5 percent of peak. The precision is within ±2％. The minimum range of system is: 1.3×10~(-5)for He, 9×10~(-5)for Ne, 8×10~(-5)for Ar. It gets rare gases isotopes ratios in air as follows: ~(40)Ar/ ~(36)Ar is 296.05, ~4He/ ~(40)Ar is 1.94 10~(-4), ~4He/ ~(20)Ne is 0.167. The mass spectrometer can be used for researches in geology, seismological gas geochemistry and so on.