Abstract: The four main factors of top-coal recovery are as followed: top-coal thickness, accumulation thickness of immediate roof falling, depositing angle of falling gauge and the distance between falling gauge and out edge of posterior conveyor. then we obtain the important order of the four main factors. The primary factor is the distance between falling gauge and out edge of posterior conveyor. The secondary factor is top-coal thickness. The third and the last factor are the depositing angle of falling gauge and the accumulation thickness of immediate roof falling.