Abstract: In recent years, a kind of new purification technology of polluted river water, the artificial floating island has been widely used.This technology is pollution-free in the whole process of the water treatment, but its negative effects on water resistance have been becoming increasingly evident. In this paper, a general physical model experiment is conducted by considering the application characteristics of floating islands in rivers. Based on the experimental data, this paper systematically analyzes the damming effect upstream of artificial floating islands, defines the damming coefficient to characterize this effect, and investigates the influential factors and changes rules of the damming effect. The methods of dimensional analysis and orthogonal design tests are used, combined with sensitivity analysis. According to the analysis, the main influencing factors of the damming effect of artificial floating islands are identified. Based on the Least Squares Method, a multiple regression analysis on the relationship between the main influencing factors and the damming coefficient is carried out and a mathematical expression is obtained. The results show that the presence of floating islands causes the phenomenon of water level enhancement upstream and water level reduction downstream. The magnitude of the damming coefficient is related to the factors of floating island size, river depth, floating island draft, river width and distance from the floating island. The damming coefficient is positively related to the Froude Number, the relative width of the floating island（the ratio of side length of floating island to channel width） and the relative draft depth（the ratio of draft depth to river depth）, respectively. And the above positive relations tend to the power functions.