The denitrogenation and desulphurization behavior during refining Ni-base superalloy in VIM by using CaO crucible was studied.It was found that the desulphurization process did not occur by only using Ca O crucible.Combining with the resul ts of XRD analysis,the desulphurization mechanism of CaO c rucible was proposed.The Al additio n had beneficial effect,and played a very important role on desulphurization.And the Ti addition had adverse effect on denitrogenation.It was a powerful measure to increase vacuum level for the denitrogenation process.