The leaching of celestite (SrSO4) with sodium sulfide (Na2S) solution was investigated from the point of strontium carbonate production. Experiments were carried out to explain the conversion mechanism of celestite to strontium disulfide (SrS2) in sodium sulfide solution. Leaching temperature was held constant and the effect of stirring rate, particle size and concentration of Na2S on the conversion of celestite were studied. The product from alkali leaching was leached with HCl to dissolve the leach product, strontium disulfide. Acidic leach liquid was, then, reacted with sodium carbonate solution to precipitate strontium carbonate. It was concluded that the conversion is based on the fact that a new compound having lower solubility is formed on the mineral surface in the system SrSO4, Na2S and H2O and that the rate of conversion mainly depends on the sodium sulfide concentration. The results showed that leaching of celestite in Na2S solution for conversion to strontium disulfide and production of strontium carbonate by using this chemical are possible processes.