An ab initio method is used to calculate the surface states of Cr(001). The method is based on the tight-binding linear muffin-tin orbitals and is formulated in real space by the recursive Green's function. It achieves self-consistency efficiently and produces good results compared with the experiment. It connects a surface state right below the Fermi level to the sharp feature in the STM spectra. The density of states of the atomic sphere in the surface layer as well as those of other layers are also shown, depicting a clear picture of the surface electronic structure.