A kind of fibrous filter made from stainless steel (SS) wire net has been developed by in our institutes. This paper is to study modeling and computing method for the fibrous filters with image effect based on the previous studies. It takes the exhaust aerosol of diesel engine as an even floating flow composed of exhaust and particulate, under the effect of electrical field force, the particulate deviate from other gas phase components and deposit on the fibers. Mathematics models for calculating the flow and the electric field, as well as the capture efficiency are given in this paper. These mathematics models are used for calculating a single fiber model.