Far-infrared and visible separation filter plays an important role in imaging spectrum technique.In this paper,a kind of separation filter used in multichannel imaging system is introduced,It can divide 0.65～1.1 μm and 8～12 μm light into two beams of light when it is used at 45 degrees on Ge base.By using OptiLayer software,we have obtained the structure of film which is easy to preparation,and determinated the reasonable technique parameters after many experiments.Finally we make the filter with well optical and physics characteristics.