ABSTRACT In recent years, a new kind of drilling fluid system with unique structure micro-foam has been developed. Compared with other drilling fluid systems, it possesses many advantages. And it has been successfully applied in hundreds of wells to drill depleted reservoirs in the world wide. The geological structure is very complex in Haita area, it is difficult to achieve the requirement of increasing drilling rate by conventional drilling methods, even can’t make footage. The micro-foam drilling fluid can apply to Haita area, and solve the drilling problems commendably, which is comprehended by studying the structure and plugging, prevent caving, speed mechanism of the micro-foam drilling fluid. Field practice indicates that micro-foam drilling fluid technology can resolve the drilling problem effectively in Haita basin. It has the extremely vital significance to improve drilling speed, discover and protect reservoir stratum, decrease the risk of circulation loss and save the drilling cost.