Abstract: This paper describes pure methane's adsorption characteristics based on the lattice theory model.The model can make a difference based on different assumptions.This model has a high precision on predicting the adsorption quantity with the absolute error of less than 0.0042 mmol/g.The determined parameters such as Г₀ and ε_s can be used to indicate the influence of temperature-pressure of methane adsorption characteristics and the development degree of micropores.The value of |ε_s| decreases with the increase of temperature,with the relationship being almost linear, Г₀ <Гmaxand Г₀ can roughly characterize the molecular adsorption state,with the value of Г₀ and |ε_s| of methane adsorption in the shale much smaller than that of the activated carbon rich in micro-pores.The discussion of the linear relationship of Y and X and the calculation of the value of ε_a show that the value of |ε_a| is smaller than |ε_s|, within the scope of P and T in this paper,|ε_a| gets alittle rise first and then decrease with the increasing temperature,at a lower temperature the ratio of ε_s and and ε_a is larger(7.05 times),but as the temperature increases,the ratio decreases and gradually becomes stable(3.37 times).The study of different types of shale on a wider scale temperature and pressure with this theory has a great significance for the shale microstructure characterization.