In order to solve the technological problems of high cost of oil-based drilling fluids, cuttings with high oil content and difficult late environmental treatment and speed up the progress of shale gas development to ease the shortage of oil and gas resources, by the laboratory experiments, an oil-based drilling fluid system with low oil-water ratio was successfully developed. This system has good rheological property, electrical stability and inhibitory property with low filtration, by which drilling fluid cost is reduced through effectively wellbore stability control and friction & torque reducing. The application of this system met the construction requirements and ensured construction safety in Baoye well-3.