The invention discloses an open mill automatic cleaning device. The open mill automatic cleaning device comprises a cleaning ring arranged on the outer side of a mill extruding roll in a sleeving mode, wherein the top of the cleaning ring is connected with a supporting frame through a connecting shaft, a shaft clutch and a clutch motor; a moving motor is further connected with the cleaning ring transversely and drives the cleaning ring to slide on the mill extruding roll reciprocally for cleaning; meanwhile, the supporting frame is fixed to a frame on the side face of a mill; and cleaning liquid is arranged in the cleaning ring, the cleaning ring is connected with the cleaning liquid through a pipeline, and a nozzle is further arranged on the part, facing the extruding roll, of the cleaning ring. The automatic cleaning device is directly arranged on the extruding roll in a sleeving mode for cleaning the extruding roll, the cleaning effect is good, and when the cleaning device is not used, the automatic cleaning device is separated by directly opening the clutch motor and can automatically clean the extruding roll under the action of the moving motor; and the cleaning device is small in occupied space, convenient to mount and use and high in automation degree.