Abstract: The broad-shallow and shifting channels in Xinjiang have characteristics of shallow water depth,steep gradients, high flow velocity and easily scoured river bed. Its backwater,due to bridge constrictions,is different from that of alluvial channels. In this paper,a simple formula is developed for estimating backwater by generalized mobile-bed river engineering model experiment. As it reflects characteristics of the broad-shallow and shifting channels in Xinjiang,author's formula fits in with this kind of rivers preferably.