Abstract: Biofilm colonization on sediment particles can have a significant effect on particle incipient motion.A series of flume experiments was conducted on two types of sediments,one of which was immersed in deionized water,and the other was cultivated in a mixture of natural water and nutrient solution.The result shows that the two sediment types can result in a significant difference in incipient motion.The incipient velocity of cultivated sediment varies over time.Sediment cultivated in natural nutritious water has a higher stability due to the biofilm growth.The incipient velocity increases with time until reaching a critical threshold,at which the optimum condition for biological activities is obtained,and then decrease.It is erect,especially in polluted water indicated that the role of microbes in sediment incipient motion needs to be consid ered,especially in polleted water bodies.