Stream blockage by the debris flow from tributary valleys is a common phenomenon in mountainous area,which takes place when large quantities of sediment transported by debris flow reaches a river channel causing its complete or partial blockage.The dam formed by debris flow may causes upstream and downstream flooding,and presents great threat to people and property.Because of the catastrophic influence on people and property,debris-flow dam has attracted many attentions from the researchers and local administration.But,lit- tle attention has been given to the quantitative interrelationships of the potential influential factors.In this pa- per,the interrelationships of important influential factors caused the stream blockage by debris flow were ana- lyzed through flume experiment,and a model to predict the blockage was presented. Stream blockage by the debris flow from tributary valleys is a common phenomenon in mountainous area may occur upstream downstream flooding, and presents great threat to people and property.Because of the catastrophic influence on people and property, debris-flow dam has attractor many attentions from the researchers and local administration.But, lit- tle attention has been given to the quantitative interrelationships of the potential influential factors. In this pa-per, the interrelationships of important influential factors caused the stream blockage by debris flow were ana- lyzed through flume experiment, and a model to predict the blockage was presented.