Abstract: Based on analysis of the working process of the KSS constant-tonnage rapid loading system and the cause leading to the reduction of the percentage of coarse coal, a study is made of the law to control the opening-closing of the sluice gate of the surge bin, and the way to improve the car loading effect. It is found that the speed of the tractor needs to be varied depending on the volume of the coal in surge bin. Through adopting effective measures, it is made possible to raise the stored coal level in the surge bin and reduce indirectly the drop height of coal during car loading, and to increase the percentage of coarse coal. It offers a simple approach for the KSS car loading system to increase the percentage of coarse coal during car loading.