Abstract: Using the large eddy simulation (LES) and the finite difference method, a three- dimensional simulation of the velocity field of flow around a square cylinder at a Reynolds number of 22 000 is conducted. The N-S equation is split into advection step, diffusion step and propagation step with the time split-operator. The near-wall effect is treated by using two-layer model, rather than the usually employed wall damping function. The convection term is discretized with upwind- central difference scheme, and the pressure equation is solved by successive over-relaxation (SOR) method. The computed mean velocity along the symmetry line is compared with experimental results reported in literatures. They are in good agreement with each other.