The pump sump is an important part of pump station. Its flow and hydraulic characteristics have an important impact on the performance of the pump. Poor flow patterns are often accompanied by hydraulic phenomena such as vortices. Vortices in the vicinity of pump intakes influence the pump performance with loss of efficiency and vibration. The vortex may appear in the pump sump, and the vortex is generally divided into free surface vortex and submerged vortex. Compared with most Reynolds averaged Navier-Stokes (RANS) based simulations, large eddy simulation (LES) showed a better prediction for all kinds of vortices on location, shape, size of vortex core, velocity, as well as the turbulence kinetic energy inside vortex core. The LES results agreed with PIV results well. Based on the numerical results, timeaveraged behavior of three typical vortices showed better similarities with reality that there was always a core region surrounding the axis where the azimuthal velocity stopped increasing and decreased to zero as radius went to zero. Besides, isosurface of λ2 was adopted to visualize the vortices. The volume of fluid model (VOF) and LES were used to simulate the vortices in the pump sump. The LES model, including the employed mesh was systematically analyzed and the numerical results were compared with the wellknown published experiment with respect to the mean velocity and vorticity fields. Particular interests were paid to discover evolution of the freesurface and wallattached vortices in term of their temporal and spatial characteristics. The anisotropic turbulence structure around the vortices were revealed as well as the momentum transport. The findings provided a deep insight into the application of LES in pump sump and the underlying mechanism of vortex formation and evolution in the sump.