The invention discloses a high resolution OLED display device and a making method thereof; the display device comprises a plurality of pixels; each pixel comprises a plurality of sub-pixels; the sub-pixels are partially overlapped so as to form intermediate color sub-pixels; the making method comprises a step of using a mask layer to evaporate the sub-pixels, so the sub-pixels can be partially overlapped, thus forming the intermediate color sub-pixels in the overlapping portion. The method overlaps the sub-pixels through evaporation, thus greatly reducing each pixel area, and greatly improving OLED resolution; in addition, the overlapping portion forms the intermediate color sub-pixels, so the intermediate color sub-pixels can directly display the intermediate color; one sub-pixel can display the color originally needing more sub-pixels in mixture, thus reducing power consumption.