The study of local scour characteristics of step-shaped spur dike is of great significance to the design of river channel regulation projects. We study the effects of inflow condition and spur dike size on local scour of step-shaped spur dike by using a 2D flow and sediment mathematical model. The results show that under the constant flow of clear water，the time required for scour to reach equilibrium is mainly affected by the inflow condition，while the geometric scale of spur dike has relatively fewer impacts. With the increase of Froude number Fr，both the area of scouring pit A and the maximum scours depth hs increase linearly. The mean scour depth increases slowly with Fr when Fr≤ 0.565，and increases relatively faster with Fr when Fr＞〖HTSS〗〖KG*3〗 0.565. The height of the first step spur dike and the length of the second step spur dike have a certain degree of equivalence in the influence of the local scour pit shape and scour depth development. Both hs and increase with the relative height of the first step spur dike ψ，and the growth tend to be flat when ψ＞0.7.