The invention provides a scanning and auto stop device for a warp machine, which comprises a warp machine body. Yarn is outputted through a yarn outlet and is wound on a yarn roller; the warp machinebody at the upper end of the yarn roller is fixedly provided with a cover plate; the bottom end of the cover plate is transversely provided with a sliding rail; a sliding block is clamped in a slidingmode in the sliding rail; one end, facing the warp machine body, of the sliding block is fixedly provided with a threaded sleeve; the threaded sleeve is internally and movably contacted with a threaded rod through a threaded structure; the bottom end of the sliding block is fixedly connected onto the upper end of a supporting rod; and the lower end of the supporting rod is fixedly provided with ascanner. Positive and negative rotation of a servo motor is controlled through a PLC, the threaded rod thus rotates on the cover plate, the threaded sleeve sleeves the threaded rod through the threaded structure, the threaded sleeve moves transversely on the threaded rod when the threaded rod rotates, the scanner moves horizontally above the yarn to scan the yarn, movement of the motor is stoppedthrough the PLC, an alarm circuit is also connected, and a worker is reminded.