The invention relates to a device for separating polyethylene terephthalate (PET) bottle caps, and discloses a bottle cap discharging auger device used for separating the PET bottle caps. The device comprises a helical auger, a groove body, an inclined scraping plate, a limiting plate, a water filtrating screen board and an inclined bottle discharging port. The helical auger is arranged in the groove body, the upper half portion of the helical auger is on the water surface, and the lower half portion of the helical auger is under the water level. The inclined scraping plate is arranged at the left end of a helical auger shaft. The limiting plate is arranged on the left side of the inclined scraping plate. The water filtrating screen board is arranged on the left side of the limiting plate. A space is arranged between the inclined scraping plate and the limiting plate, and water in the space flows back into the groove body; while, the bottle caps are picked up from the water surface under the action of the inclined scraping plate and drop into the water filtrating screen board after arriving at the limiting plate. Auger blades of the helical auger extend into the water filtrating screen board. The inclined bottle discharging port is formed in the right side end of the water filtrating screen board. The bottle cap discharging auger device used for separating the PET bottle caps can effectively remove the water content of propene polymer (PP) and has the characteristics of being good in separating effect and high in efficiency.