Sedimentary transport of Xiaojiang River was analyzed by a case study of debris flow in Jiangjia gully on August 4,2009.The entrance of debris flow into the river greatly changed the characteristics of suspended sediment transport,in comparison with the observation data during the rainy season.The sediment concentration increased from 4.00 kg/m³ to 25.78 kg/m³ after the confluence of debris flow,yet the grain composition remained almost the same.Furthermore,granular analysis was conducted on the slurry of debris flow and the suspended sediment at the Xiaojiang bridge and Xintian dam,the results showed that the suspended sediment at Xintian Dam mostly came from the debris flow,resulting in the smaller average grain-size parameters(the maximum value decreased from 7.460 μm to 7.097 μm),but the sorting of them had been enhanced and fell into the medium-sorting.Simultaneously,we noticed that there was still a clear distinction between the sediment slurry of water and debris flow.