In view of the lack of theoretical basis for determining the layout parameters of the deep trench bottom protection belt,a large area semi-river normal model is used to study the influence on water level under different bottom protection parameters of the Qixingtai deep trench bottom protection belt,and the conclusion that the optimal plane spacing of the Qixingtai deep trench bottom protection belt is 300~330 m is obtained.The backwater law of strip-shaped bottom protection belt is put forward,which can provide the basis for the determination of similar deep trench bottom protection belt spacing.Through the research on the influence of the bottom protection belt on the traceability of water level decline,it is revealed that the bottom protection mainly aims to maintain the water level stability of the river section through two aspects：1） shaping the riverbed bulge to increase the riverbed shape resistance and affecting traceability transmission characteristics of water level decline；2） restraining the riverbed scouring and undercutting.