Abstract: The numerical method was employed to study the effect of technological factors on the inclusion removal in RH degasser. The numerical results indicated that for small inclusion, the number density can be decreased effectively by collision growth. For big inclusion, the number density can be decreased by Stokes floatation. The inserting depth of the snorkels, the vacuum chamber pressure and the gas flow rate are three key parameters of inclusion removal and the gas flow rate is the most important one. The inclusion removal rate is up 6 percent while the inserting depth of the snorkels decreases from 800mm to 300mm. The inclusion removal rate is up 12 percent while the vacuum chamber pressure decreases from 5.0kPa to 1.0kPa. The inclusion removal rate can reach 75 percent while the gas flow rate is up to 2000NL. Inclusions larger than 20μm can be removed after RH treatment if gas flow rate is up to 1275NL, but it can not promote the removal rate of inclusions greater than 10μm effectively if the gas flow rate is greater than 1750NL.