Changning shale gas block is located between the low steep tectonic belt of Sichuan South and Loushan fold belt in Sichuan Basin, affected by the surface karst landform and accumulation body, the surface drilling leakage and collapse are serious, and the environmental protection pressure is high; the middle and lower strata are affected by the underground faults, fracture development, low pressure-bearing capacity and other complex geological conditions, the wells leak seriously, and the window of safe density of the drilling fluids is narrow, the leakage of spraying and collapsing exist at the same time. There are multiple leakage layers from top to bottom of the well, and it is difficult to plug the leakage on site with low success rate. By analysing the actual drilling data of the neighbouring wells and summarizing the construction experience, the team selected a bridge plugging synergist and a bag-type plugging agent to enhance the effect of bridge plugging, and at the same time, optimized the on-site plugging procedures and processes, forming a technical plan for leakage prevention and plugging in Changning shale gas block, which was popularized and applied in the Ning 209 block. The success rate of one-time plugging of water-based drilling fluid leakage in the upper Maokou-Qixia Formation was increased by 42%, and the oil-based drilling fluid leakage in the target layer Longmaxi-Wufeng Formation decreased by 70%.