When water flows past the pile group,there will be a descending water flow and a horseshoe shaped vortex in front of the pile,which significantly strengthens the sediment carrying capacity and transport capacity of the water flow.Based on the local scour flume experiment of unsteady flow pile group,this paper studies the local scour distribution and maximum scour depth of pile group under unsteady flow.By using computational fluid dynamics software Flow 3D to simulate and calculate the flume experiment,and investigate the development process of local scouring around the pile group under unsteady flow.The research shows that the scouring range of upstream single piles is from 2D in front of the pile(Pile diameter) to 1D behind the pile,and from 2.5D on the outside of the pile to 1D on the inside of the pile.The scouring range of downstream single piles is from 1D in front of the pile to 1D behind the pile,and from 1.5D on the outside of the pile to 1D on the inside of the pile.Additionally,there are differences in the transverse scouring sections in various areas of the pile group.The maximum scouring depth and scouring volume increase logarithmically with time until the scour equilibrium is reached.Moreover,20% of the time for local erosion can achieve 50% of the scouring equilibrium state,and 50% of the time can reach 80% of the scouring equilibrium state.