Fibrous filters such as nonwoven media are generally characterized by their collection efficiency and pressure drop. The traditional computational studies in this area typically based on unrealistic over-simplified geometries with the fibers placed in a lattice perpendicular to the flow.This paper describes the filter properties made of different Nonwoven materials by using Computational Fluid Dynanics (CFD) approach. In this study, for the first time, a virtual 3 - D web is generated based on the fiber orientation information obtaining from analyzing microscopic images of both long-fiber and short-fiber nonwoven structures. Pressure drop and collection efficiency of our virtual filter are simulated and compared with the previous analytical and numerical models as well as experiment.