Abstract: The molecule diameter of nitrogen and methane is similar and the separation technology is one of the technical problems for the development of low concentration coal-bed gas concentration technology. In this paper, two stage pressure swing adsorption (PSA) was applied for the separation and purification of low concentration coal-bed methane and nitrogen. Selecting special carbon molecular sieve for silazane separation and integrated innovation of carbon molecular sieve filling process, at the same time, to balance the relationship between separation performance and process cost, the same structure design and different mixing proportion design of carbon molecular sieve is combined to finally complete coal-bed mathe silazane separation process design. Field practice shows that two stage pressure swing adsorption concentration technology can enrich CH₄ concentration of 24% raw material gas step by step, gradually from 51% to 86% and methane recovery rate of CH₄ is more than 65%, which achieves the separation concentration and purification of N₂ and CH₄ of low concentration coal-bed gas, and creates conditions for the use of low concentration coal-bed gas.