Abstract: To investigate the adsorption and diffusion mechanisms of methane and helium in shale kerogen and clarify the occurrence state of mixed gas components, this study takes Longmaxi Formation shale in Weiyuan area as the research object, constructs the nanoscale pore structure of kerogen, and quantitatively characterizes the adsorption and diffusion behaviors of the mixed gas system by means of molecular simulation, clarifies the effect of temperature on gas diffusion, and discusses the differential enrichment mechanism of associated helium in Weiyuan shale gas field. The results show that: (1) For different gas components, the adsorption heat of methane is four times that of helium, indicating that methane has a stronger adsorption capacity than helium; however, the adsorption heats of both gases are less than 5 kcal/mol, suggesting that they predominantly exist in a free state within kerogen pores. (2) The diffusion coefficient of helium is consistently higher than that of methane, but the diffusion rate is subject to a threshold effect. When the helium concentration exceeds 80%, the excessively low methane content in kerogen pores leads to a reduction of diffusion driving force, thereby decreasing the diffusion rates of both gases. (3) During the burial process of Longmaxi Formation shale in Weiyuan area, increasing formation temperature promotes massive desorption of adsorbed methane and accelerates the gas diffusion rate. During tectonic uplift, the dilution effect of methane on helium is relatively weakened, and helium tends to be enriched in the micro-nanoscale pores of tectonic highs. This study reveals the coupled adsorption-diffusion mechanism of methane and helium in Longmaxi Formation shale of Weiyuan area from the micro-to-macro scale, providing theoretical support for the differential enrichment analysis of helium in shale.