Coal reservoirs have a complex pore structure, which is accompanied by energy changes during the adsorption of methane gas. To study the heterogeneity of energy changes during the pore and methane adsorption processes in coal reservoirs, fractal dimension analysis is employed to analyze the heterogeneity of coal pores. The heterogeneity of energy changes during the isothermal adsorption process is analyzed using adsorption potential and surface free energy theory. The results show that sample PY-1, PB-1, and PB-2 mainly develop micropores, while sample PY-2 mainly develops macropores, and the pore distribution of different samples is significantly different. Micropores are the main sites for methane adsorption, but not the determining factor affecting methane adsorption. Coal's pore structure and inherent properties exert a significant influence on the heterogeneity of methane adsorption. As the vitrinite content increases, the complexity of pore structure and the fractal dimension of pores also increase, leading to enhanced heterogeneity. Consequently, methane adsorption exhibits higher uptake, accompanied by more pronounced variations in adsorption potential and surface free energy.