Abstract: The decisive factors of belt conveyor's transport capacity are analyzed. The model that bulk materials loads on the belt and achieves mechanical equilibrium is established by using the discrete element numerical simulation method. According to research of several groups of bulk materials with different grain composition，the influence of the mean particle size，the range of particle size on the belt conveyor transport capacity is analyzed. The result shows that the bigger the mean particle size is，the bigger the ratio of maximum particle to minimum particle is，and the bigger the area of the cross section of bulk solid loading on the belt conveyor is. Therefore，the belt conveyor owns a larger transport capacity.

Key words: Belt conveyor, Transport capacity, Grain composition