Abstract: In this paper,flow boundary water levels along flood embankments in flood plain reach of the Songhuajiang River are studied by the physical model. Different modeling methods to the roughness of the flood plain were used. Based on the similar model,the relationships between the water levels along the flood embankments and the discharges are measured. The experimental results show that due to the complex resistance in the reach,the water levels along the embankments are different to the levels of the main channel at the same section,and the maximum difference between the two places is 0.3 m.