Abstract: Methanogen is a kind of strictly anaerobic archaea that can transform organic matter and inorganic compounds into methane and carbon dioxide in an anaerobic fermentation. Methanogenesis usually occurs in the last step of anaerobic fermentation process. Being the key part of the nature carbon cycle，end-product of methane has been ranked as a second key greenhouse gas besides carbon dioxide which exacerbate global warming trend. In order to obtain a further understanding to the biological characteristics of different kinds of methanogens，researches on laboratorial techniques of isolating and purifying methanogens are also increasingly focused in last decades. This paper thoroughly reviewed research advances on typical habitat and biological role of methanogens，species classification and their physiological characteristics with focuses on techniques of strains isolation and purification，and the selective action of various mediums for methanogens.

Key words: methanogen; isolation and purification; selective mediums