This paper analyzes the influence on the functions for navigation,water diversion and drainage of Jiuweigang river caused by the construction of the proposed bridge by 2D numerical simulation model.The main conclusions are:1)The impact of the bridge construction on the navigable flow conditions would be minimal and the navigable clearance height would meet the demand,but the navigable clearance width wouldn’t meet the demand when the water level is low;2)More attention should be paid to the safety of the right bank of the river for the increasing flow velocity.The impact of the piers should be decreased by some optimized improvement measures.