The reflection on the semi-infinite periodic one-dimensional photonic crystal composed of alternate layers of ordinary material and negative refraction material is investigated. We find that the reflectivity is exactly equal to 1 in the forbidden frequency gap, and in the pass band, it averages out the rapid fluctuation of reflection of the finite structure. When the optical thickness of both ordinary material and negative refraction material are in opposite sign, there will be a zero-n band gap. We analytically prove that the zero-n band gap is insensitive to incident angle and polarization. It is also anticipated that the zero-n band gap is invariant with the scaling of lattice constant.