Adsorbed gas represents a primary mode of shale gas occurrence and is a major source of shale gas production in the later stages of development. It primarily resides within the organic kerogen and clay minerals of shale formations

with organic kerogen being the dominant host. Consequently

the study of organic kerogen characteristics and its adsorption mechanisms is crucial for understanding shale gas development. In this paper

the kerogen of Longmaxi Shale in

the Sichuan Basin is taken as the research object. The microstructure of kerogen is expressed by combining methods through the solid-state NMR experiment

Fourier transform infrared spectroscopy experiment

X-ray photoelectron spectroscopy experiment

and the molecular structure model of kerogen is constructed. The adsorption mechanism and characteristics of CH

4

in kerogen of Longmaxi Shale are analyzed by magnetic levitation weight experiment

molecular simulation methods of the Grand Canonical Monte Carlo（GCMC）

and Molecular Dynamics（MD）. The results show that the molecular formula of the kerogen of shale experimental sample of Longmaxi Formation is C

237

H

219

O

21

N

5

S

4

. The excess adsorption gas volume of CH

4

in kerogen increase first and then decreased with the increase of pressure. Under the same pore size and pressure

the excess adsorption gas volume and total gas volume of CH

4

decrease with the increase in temperature. The C and S atoms in kerogen are the main cause of CH

4

adsorption. The CH

4

near the kerogen pore wall presents an adsorption state

while the CH

4

far from the kerogen pore wall presents a free state. As the pore size increase

the distance between the two peaks of CH

4

density gradually increases

and the peak value decreases gradually.