According to the analysis of grain size, mineral compositions and materials corapped by quartz in the suspended and bed loads sampled from the Changjiang River and the Yellow River, this paper reveals the difference of load's compositions between the two rivers. In the Yellow River the sizes of suspended loads are coarser than the Changjiang River, but the bed loads are finer. Among the mineral compositions, the biotite content of the Yellow River's loads in much more than the Changjiang River's, and its monomorillonite content in the clay minerals is over one time more than the Changjiang River's. All this reflects the effects of material sources and the hydraulic conditions on loads characters. The analysis of materials corapped by quartz indicates the environmental difference of material sources between the two rivers. It provides a new method for marking off the loads sources.