Abstract: The experimental research on the optimization of leaching conditions is necessary for the all-sliming cyanide leaching operation in a gold mine in Inner Mongolia due to the change of raw ore properties.Based on the results of process mineralogy,the effects of CaO dosage,NaCN dosage and aeration rate on gold leaching rate were investigated by Response Surface Methodology and fitting formula and response surface are established.The results show that CaO dosage,NaCN dosage and aeration rate could affect gold leaching rate significantly and these three factors had serious interaction effect.The leaching rate is estimated to reach 94.75 % under the optimized conditions that particles smaller than 74 μm accounts for 90 %,CaO dosage is 3.330 kg/t,NaCN dosage is 1.040 kg/t and aeration rate is 0.076 m3/h.This study provides technical basis for the practical process optimization.