Abstract: [Objective] The exploration potential of natural gas in the Lower Permian Fengcheng Formation in the western Central Depression of the Junggar Basin has been gradually clarified, and a breakthrough in ultra-deep natural gas exploration has been achieved. However, studies on the adsorption characteristics and controlling factors of ultra-deep shale gas in the Fengcheng Formation remain limited. [Methods] Taking the ultra- deep Fengcheng Formation shale in the Well Pen-1 West Sag as the research object, this study systematically investigates its pore structure, shale gas adsorption characteristics, and controlling factors through integrated analyses, including basic geochemical analysis, field emission scanning electron microscopy (FE-SEM) observation, full-aperture pore structure characterization, spontaneous imbibition experiments, and methane isothermal adsorption experiments. [Results] The results indicate that the Fengcheng Formation shale in the study area primarily develops three lithofacies: mixed, clayey, and felsic shale. All lithofacies are dominated by inorganic pores, among which secondary clay mineral pores are the main type, accounting for over 70% of the surface porosity. The FE-SEM observation reveals the development of macropores, particularly clay mineral macropores, while full-aperture pore structure analysis shows that mesopores are the dominant pore type. The comparison between these results suggests that clay mineral pores are largely disconnected, whereas organic pores, despite their low proportion in total surface porosity, exhibit good connectivity. Methane adsorption experiments demonstrate that the adsorption capacity of mixed and clayey shales is generally higher than that of felsic shales. [Conclusion] Further analysis of pore structure parameters indicates that pore volume, specific surface area, and fractal dimension have weak correlations with adsorption capacity, while pore connectivity serves as the key structural parameter controlling shale gas adsorption. Analysis of the controlling effects of shale components on adsorption characteristics reveals that organic matter abundance is the primary factor influencing the adsorption capacity of the Fengcheng Formation shale, with inorganic minerals playing a limited role. These research findings provide a theoretical basis and scientific support for the exploration and development of ultra-deep shale gas in the Fengcheng Formation of the Well Pen-1 West Sag, Junggar Basin.