Abstract: Based on a systematic analysis on coal reservoir adsorption data,the empirical regression formula is established,which corrects adsorption isothermal curves of coal samples(moisture-free basis)for conditions of equilibrium moisture content and reservoir temperature.Accordingly the regional and vertical distribution regularities of isothermal adsorption contents(a,b values)of coal reservoirs in different geological time and dfferent coal ranks in China,as well as their effect on coalbed gas surface development.