The progress of researches on the scalar scattering theory is reviewed briefly, and the one-dimensional scattering theory presented by Beckmann and several typical scattering models such as the uncorrelated surface roughness model, the additive surface roughness and the uncorrelated bulk inhomogeneity model are introduced. Scattering properties of 11-layer reflector centered at 632.8nm under those models are compared. It is shown that the scattering at the band edges are due almost entirely to the uncorrelated layer thickness, while the scattering in the reflection band results from the additive surface roughness. The scattering caused by idea roughness in the reflection band is quite small and drops to a near zero value at the band edges.