The strata of Ajile Pb-Zn mine are complex in Dongwu Banner of Inner Mongolia and multiple tectonic fracture zones were encountered in drilling process. Tuff and carbonaceous slate are the main components of the strata with alteration developing; water swelling and hydration dispersed were extremely easy to happen in muddy and siliceous cement segments, which caused lots of wall problems such as collapsing, necking and so on. In the case that the effects of a variety of flushing fluid are not ideal, the test and application were made on the low solid plant gum drilling fluid, good anti-sloughing effect was achieved with strong adaptability and moderate viscosity, the thin mud-cake formed was dense and flexible to successfully solve the wall protection in this mining area. Taking the example of ZK1507, the paper describes the obvious anti-sloughing effect of the drilling fluid used in the water sensitive strata, which could be applied in the actual production.