Abstract: In order to understand the geological gas-controlling functions in the coalbeds of the Middle Jurassic Xishanyao formation in western Fukang block, Junggar basin, the block is divided into 2 structural units according to the regional hydrogeological boundary--Chigang reverse fault and CBM-rich units are classified based on methane weathering zone and hydrogeological conditions. Based on the analysis of structural and hydrogeological features, the paper discusses the coupled structural-hydrogeological gas-controlling mechanism. The study results show that the enrichment of CBM in the Xishanyao formation of western Fukang block should be the product of the coupled functions of structure and hydrogeology conditions. Tectonic movements resulted in dynamic metamorphism and plutonic metamorphism in coalbeds, which are helpful for the generation of thermogenic gas; the sealed folds and thrust faults resulted from horizontal compression in the late Yanshan movement and Himalayan movement contributed to CBM preservation, whereas the tectonic uplift in the early Yanshan movement was not conductive to primary biogenic gas preservation; CBM accumulation by hydraulic seal occurred due to the lateral charging of groundwater into the stagnation areas with high salinity. CBM losses in the coalbeds with the burial depth lower than 600 m in the middle-upper Xishanyao formation were caused by tectonic uplift, relatively strong seasonal runoff and evaporation. Meanwhile, high-salinity formation water due to arid climate restrained the generation of secondary biogenic gas, resulting in the low content of CBM