The basic mechanism and kinetics of the transformation process of alumina inclusions in steel was reported when calcium introduced into the steel by wire feeding or powder injection. To clarify the mechanisms model, experiments were performed by studying reactions between Al2O3 and CaO in a laboratory furnace and by performing calcium treatments in an 8kg induction furnace for Al deoxidised melt. The phases formed during the reaction between Al2O3 and CaO were examined by SEM-EDS (scanning electron microscope-energy dispersive spectrometer), and the reaction sequence of Al2O3 (→) CA6 (→) CA2 (→) CA (→) CAx(l) was discussed in term of the experimental observations. The kinetics of the reaction of calcium with alumina inclusions were simulated by immersing alumina plates in a Ca treated steel melt in the induction furnace. Results were compared with observations of real inclusion transformation. A kinetic model was proposed based on the results.