Using Coal gangue as cemented filling material can reduce filling cost and is beneficial to the protection in mine.However,coal gangue particle usually is the first to settle in agitator because its larger particle size and higher heterogeneous coefficient,so greatly affect the agitation effect of filling slurry.The preparation process of filling slurry was investigated,and it was found that the settling rate of coal gangue particle in uniform slurry of cement and fly ash is lower than in water.On the basis of this characteristic,the entering order optimization of filling materials is put forward.