An immersed boundary method was applied to numerical simulation of the flow past a clean/iced NACA0012 airfoil.In this paper, two dimension imcompressible Reynolds-averaged Navier-Stokes equations were solved with SIMPLEC method.One equation turbulence model——Spalart-Allmaras turbulence model, was used in the numerical procedure.Good agreement was found between the present numerical results and previous experimental work.