Abstract: With three typical natural river courses in China as case study, we preliminarily discussed the characteristics and formation conditions of discontinuous widely-graded sediment,  providing basis for researching discontinuous widely-graded bed load transport. It's believed that the characteristics of discontinuous widely-graded sediment are as follows: the sediment particle size varies in a wide range; sediment of a certain size is in a small amount or even in absence; and the weight percent of bed sediment exhibits a clear bimodal distribution. The formation of discontinuous widely-graded sediment is based on three conditions: non-uniform bed sediments and thick riverbed cover, sediment supplies from the upstream, and varying flow velocity in the river course.

Key words: discontinuous widely-graded sediment, sediment characteristic, sediment particle size, formation condition