Abstract: In recent years, oil-based drilling fluid system has been adopted in the East China Sea development wells to solve many problems, such as difficulty in wellbore cleaning, high friction and torque, wellbore instability in high angle directional wells and extended reach wells. Compared with water-based drilling fluid, oil-based drilling fluid has stronger inhibition and better lubricity, which is conducive to maintaining wellbore stability and reducing the occurrence frequency of drilling tool sticking accidents.Firstly, the drilled development wells using oil-base drilling fluid in the East China Sea oil and gas fields were analyzed and studied, and then the applicability of oil-base drilling fluid in the East China Sea exploration wells and its waste oil removal and treatment methods were studied theoretically, and a set of oil-based drilling fluid application process and method suitable for the East China Sea exploration wells were summarized. The results of field application show that this set of technology is feasible, meets the requirements of offshore environmental protection, and is conducive to achieving the safe and efficient drilling target of exploration wells in the East China Sea.