Energetic heavy ion passing through polymeiic materials can produce a cylindrical intensively damaged area along the ion path, which is referred to as latent ion track. Large amount of small molecule fragments are produced inside ion track through interactions between the ion and the target atoms, which made it easy to be chemically etched compared to the bulk material. Porous membranes with nanometer and micrometer sized pores can therefore be produced through proper etching of the ion irradiated polymer film. As the pores are well aligned with respect to each other and the pore geometric shape can be finely controlled, the so produced ion track membrane has found wide applications.