Shale gas mainly deposits in marine, continental and transitional facies in mud shale with adsorption and free state, the different deposition process, time and type of the rocks show the anisotropic of physical and chemical properties of strata or rocks. The formations of shale gas drilling mainly include mudstone, sandstone, argillaceous sandstone, sandy mudstone and so on in different times and these rocks have strong sensitivity to water molecules in drilling fluid, therefore a lot of time was spent to deal with difficult tripping, large amount of sentiments, repeated breaking and pipe sticking during the drilling process, the pure drilling time was reduced. The basic reasons of these problems were the diameter shrinkage and oversize caused by rock expansion and wall collapse respectively. This paper describes the formation characteristics of Zhongmou shale gas block firstly, and then the research and analysis on the drilling problems of Mouye well No.1 are made in borehole diameter shrinkage and oversize, the principled suggestions are put forward for drilling fluid and drilling technology selection.