On the basis of Drude theory,the relationship of refractive index and the deposition rate ,which were changeable in the course of deposition of inhomogeneous coatings,was discussed firstly.Then using computer aided simulation,the optical characteristics of inhomogeneous dielectric coatings,which was mixture of different materials from different evaporated sources,was also discussed.The discussion included single period and multi-periods,positive change and negative change,integral and half-baked periods,etc.The minimum of transmittance attenuated by thrice polynomial of periods was discovered,and the negative Drude inhomogeneous coatings with half-baked periods was the optimization design of Notch filters.