To study the local scour characteristics and flow field features of submerged square piles under the effect of different flow intensity, a series of local scour tests were carried out around the pile foundation with the non-uniform sand, and numerical tests were conducted to analyze the scour topography, change law of scour depth and flow turbulence around the square pile. The flow field around the pile were simulated by OpenFOAM. Thereafter, this study discussed the distribution characteristics of horseshoe vortex at the upstream of pile, backflow and downflow around the pile. The results show that the depth of scouring pits, the height of dunes and their sizes around the piles all increase with the increasing of flow intensity under the clear-water scour condition. In the equilibrium scouring terrain, flow around the pile is very complicated, and the turbulence energy in the scour pit becomes larger with the increasing flow intensity value. When the flow intensity is close to 1.0, the shielding effect of coarse-grained sediment on fine particles affects the maximum scour depth of pile perimeter to some extent; thus, the eddy current intensity in the scour pit in front of pile will be enhanced, resulting in more complicated flow behaviour in the scour pit.