Alumina of smelting reduction calcium aluminate slag was leached by sodium carbonate solutions. The effects of Na2Oc concentration, reaction temperature，reaction time，liquid-solid ratio on the leaching rate of alumina were investigated and its leaching kinetics was studied as well. The results show that the optimum conditions of leaching are as follows: reaction temperature of 75 ℃, Na2Oc concentration of 100g/L，reaction time of 100min，liquid-solid ratio of 4.5:1. The leaching rate of alumina is 83.7% under the optimum conditions. It is found that the leaching process can be satisfactorily represented by fitting with Avrami equation. The apparent activation energy of leaching process and the feature parameter of Avrami equation are determined to be 11.844 kJ•mol-1 and 0.0983, respectively, the leaching process is inner-difussion controlled.