To realize the injection and production technology in the same well for high-water-cut oil wells, the multicup isoflux oil-water separator was optimized and designed according to the separation principle similar to multicup isoflux gas anchor. In the design process, the number of openings and apertures in each layer of the separator increased step by step from top to bottom, the liquid intake of each liquid inlet was similar, and the residence time of each produced liquid in the separator was long enough. Through the analysis of the optimal combination of different segmentation methods, the number of openings and different apertures, considering the requirements of machining, parameters such as aperture size, aperture classification and the number of openings were optimized according to the principle of fluid dynamics. While ensuring that the residence time of produced liquid in the settling cups at each part exceeds 150s, this design gives full play to the role of settling cups, effectively shortens the length of downhole oil-water separator, and saves production and operating costs.