A well known property of topological insulators is the existence of robust edge states. We use the SSH model to illustrate the robustness of the zero energy edge state under arbitrary perturbations. Also, it is known that the polarization is proportional to the Zak phase. By summing over the Zak phase of all the energy bands, the total Zak phase is shown to be always an integer multiple of 2pi even if there is no chiral symmetry. Therefore, we may relate the total Zak phase and the winding number, and we may generalize the bulk-edge correspondence to systems without chiral symmetry.