The invention discloses a wire break detection device based on a wire break protection circuit. The wire break detection device comprises a sliding block mounted in a wire tightening device, an induction switch mounted above the end B of the wire tightening device and the wire break protection circuit based on the induction switch and the sliding block. When no molybdenum wire is mounted in the wire tightening device, the sliding block is locked at the end A of the wire tightening device, the induction switch is not triggered, and a wire conveying motor loop is switched on. When a molybdenum wire is mounted in the wire tightening device, and the wire tightening device is in a wire tightening state or operates normally, the sliding block moves to the middle portion of the wire tightening device, the induction switch is not triggered, and the wire conveying motor loop is switched on. After the molybdenum wire in the wire tightening device is broken, the sliding block moves to the end B of the wire tightening device, the induction switch is triggered, and the wire conveying motor loop is switched off. By means of this manner, according to the wire break detection device, the wire break condition can be accurately judged, it is ensured that shutdown can be immediately achieved after wire breaking, and stability and reliability are achieved.