Abstract: In order to investigate the effect of the shapes of organic matter pores on occurrence states of methane, the carbon-based elliptical pore and the heteromorphic pores with the characteristics of protrusion and depression were established more consistently with the fact. The occurrence states of methane were simulated by using the molecular dynamics method under the temperature and pressure of gas reservoir. The simulation results show that the density of the first adsorption layer in elliptical pore (peak 0.565 g/cm3) is smaller than that of the first adsorption layer in circular pore (peak 0.620 g/cm3), and the density of the second adsorption layer in elliptical pore (peak 0.482 g/cm3) is larger than that of the second adsorption layer in circular pore (peak 0.408 g/cm3). Methane accumulated in the protrudent parts of“protrusion”pores and“depression”pores, and there is a vacancy near methane accumulation because of the atoms potential of wall. The first adsorption layer breaks which caused by the vacancy. The degree of breakage is influenced by the curvature radius of the feature point, and the degrees of breakage in“protrusion”pores are more obvious than those in“depression” pores. At the same time, it is found that the mean density of“protrusion” pores is higher than that of“depression”pores. The characteristics of free gas in the pores are influenced by the shapes of the pores. In the“protrusion”pores, with the curvature radius of feature point decrease, the free gas gradually decreases until almost disappears. In the“depression” pores, with the curvature radius of feature point decrease, second adsorption layer of methane in depression part gradually move towards non depression part, and finally, the second adsorption layers of two parts overlap, and the free gas in the pores almost disappears. The results show that the mean density and distribution pattern of methane is definitely affected by the pore shape that the occurrence states of methane are closely related to the pore shapes.