The first commercial gas separation membrane and its module in Korea produced by innovative research and self-development of Airrane in 2001.Our membrane modules have widespread in various applications such as air separation(O2/N2),dehumidification from compressed air,carbon dioxide separation(biogas,syngas,natural gas,flue gas) and VOCs separation etc.In this paper we introduce the applications of membrane process for bio gas upgrading.Biogas is a kind of new renewable energy and environmentally friendly fuel produced by bacterial conversion of organic matter under anaerobic conditions[1].Biogas composed with 50~65mol.% methane,50~35mol.% carbon dioxide,traces of hydrogen sulphide and water vapor[2].Biogas upgrading methods have been developed by using absorption process(water or chemical scrubbing process),adsorption process(pressure swing adsorption process),membrane process and hybrid process[ 3].In this study,polysulfone hollow fiber membrane was applied to biogas upgrading process.The membrane was prepared through the dry-wet spinning process and the membrane module was prepared to check the the performance of permeance and selectivity of carbon dioxide and methane[4,5].The membrane module test was focused on enhancing methane concentration from biogas with various operating conditions.A single stage module concentrated over 90% of methane as a final concentration and over 30% loss of methane.To reduce the loss of methane,multi-stage process was designed and tested and the result showed more than 95% purity of methane with less than 5% loss of methane.This paper describes the membrane process design for biogas upgrading and its optimized operating conditions were also described.