When the oilfield enters the middle and late stages of development, the moisture content of the produced liquid rises sharply. The primary problem that needs to be solved in the later stage of development is how to reduce the water content and improve the recovery rate. Hydrocyclone technology, gravity separation technology or other oil-water separation processes are used for downhole oil-water separation to achieve pre-separation of the moisture liquid downhole, so as to produce a lower water-water mixture, which has great application prospects for high water-cut oilfields. Through the brief analysis and summary of the research status of downhole oil-water separation device, the problems and challenges of the current downhole oil-water separation device were pointed out, and the prospect was made to provide a certain reference for its development.