According to the stratigraphic data of Northeast Yunnan， the limestone of Maokou formation of Permian in this area is very broken， and there are risks of well leakage， hole collapse and drilling tool blow-off. Casing wall protection method was adopted in the past drilling construction in this area， which has high cost and labor intensity. The introduction of X-A film-forming mud system during the construction of Yundi-4 well has a good effect on restraining and balancing the retaining wall of Maokou limestone formation such as loss of block， collapse and imbalance of formation pressure. All kinds of possible engineering risks are effectively solved and good economic benefits are obtained.