Spur dikes are widely used as regulating structures in inland waterway regulation projects,but their damage phenomenon is very common.Natural water flow is basically unsteady,and different unsteady conditions have different impacts on local scour around spur dikes.The RNGk-ε turbulence model and VOF (volume of fluid) model in FLOW-3D are used to study the effect of unsteady water flow on local scour around spur dikes.The results show that increasing flow variability increases the length and width of the scour hole and the maximum scour depth at the head of the dam,and will also causes the scour width to reach the critical width more quickly.The number of flood peaks affects the formation process of the maximum depth of the scour hole,and the later the flood peak appears,the smaller the development rate of the maximum scour depth.The length and area of the scour hole are not significantly related to the number of flood peaks,but the greater the number of flood peaks,the faster the scour hole width will reach the critical value.The longer the duration of the flood,the slower the rate of increase of the maximum depth of the scour hole,which eventually reaches the critical value.The longer the flood duration,the larger the length and area of the washout pit,and the later the width of the washout pit reaches the critical value.The research results can provide technical support for maintaining the stability of spur dikes during flooding.