Abstract: The determination of CaO content in columbite and steel cinder with flame atomic absorption spectrometry is studied. EDTA+TEA is used to eliminate the interferences, in HCl media, with La as releaser.The methods of sample treatment and the CaO in remainder undissolved in acids have been conducted. The result of the determina-determination and recovery of CaO shows that the ho of recovery is 100%~102 %, R.S.D<2 %.