Abstract: In order to analyse the effect of temperature, water content, particle size and metamorphic grade of coal on methane adsorption, methane adsorption ex periment was conducted with orthogonal experiment design and adsorption constants detector. The relationship between Langmuir adsorption constant a and b and the different factors, and the adsorption constant a varied with four factors were obtained by using multiple factors variance analysis and regression analysis. The results sh owed that coal samples adsorption under the action of multiple factors met Langmuir monolayer adsorption theory. Every single factor would affect Langmuir adsorption constant a and b, but influence extent was different. Metamorphic degree affected constant a was the strongest in the whole factors, followed by the temperature and pa rticle size, and water content was the last. Metamorphic degree affected the adsorption b was the strongest, followed by water content, the temperature and particle siz e was the weakest. Constant a was in positive correlation with metamorphic degree and in negative correlation with temperature, water content and the particle size, bu t constant b was in positive correlation with metamorphic degree, in negative correlation with temperature and changed periodically when particle size and water conten t changing. According the research of the methane adsorption under the action of various factors, the experimental results could provide theoretical basis on further stu dy on adsorption characteristics of coal and theoretical direction for preventing coal and gas outburst in process of mining.