Adopting model test research method,we observe the damage process of the spur dike’s root under different flow,different water depth and different length of the spur dike,analyze comparatively the damage degree of the dike root in different working conditions,and find out the damage causes of the spur dike’s root in the Upper Yangtze River.The experimental result shows that the flow is the direct factor for the washout,the length of spur dike affects the flow around the dam indirectly through affecting the flow structure surrounding the dam,and the water depth influences the root damage only when it is just submerged.When the water depth is 3 cm above the dam,the washout phenomenon is not obvious