A JK 13 across flow CW 2 kW CO 2 laser of tube plan low gas pressure discharge structure, using argon helium mixing gas, was studied. The substituted amount of He gas (Ar doped amount) increased from 20% to 60%. When the working gas pressures were 2.93~4.26 kPa and the discharge currents were 3~11 A, the laser discharged steadly and operated normally. An output power of 1.7 kW and an effciency of electro optic conversion of 16 percent can be obtained.