Drilling the mudstone of the Shihezi Formation in the Sulige Block is prone to complex issues such as lost circulation，frequent sticking and jamming during tripping，and wellbore collapse，which severely restrains the operation efficiency of drilling. To tackle the technical challenge of wellbore instability in drilling the Shihezi Formation mudstone，the mechanisms behind wellbore instability of this block were investigated by collecting samples of the Shihezi Formation mudstone and researching the microscopic fabrics and physical and chemical properties of rocks as well as the law governing the effect of hydration on rock mechanics parameters. Meanwhile，the variations of samples in the microscopic morphology，mechanical property and dispersion capability were observed after they are treated by aqueous solutions of different inhibitors and different drilling fluid systems. It was found that，on the basis of a composite salt system，the combined use of organic and inorganic inhibitors to suppress shale hydration achieved the best performance in improving wellbore stability of the Shihezi Formation mudstone. Correspondingly，countermeasures to enhance wellbore stability were proposed. The findings of this research provide theoretical support for techniques improving wellbore stability in the Sulige Block and assist in the safe，steady，and efficient development of the Sulige self-operated block.