A new optical-filter structure consisted of a number of pieces of 1-D photonic crystals, each of which with a different lattice constant, and its operation mechanism are presented. Numerical and experimental studies are performed and their results are in good accordance with each other. This structure can be applied to build different kind of filters, such as low-pass filters, band-pass filters, narrow-band-pass filters and high-pass filters, etc. Extraordinary wide band-stop and extremely narrow band-pass filters can be easily realized with such a structure.