The invention discloses a rolling mill self-excited vibration identification and alarm device. The device comprises a detecting head, a signal processing system and a display system; the display system comprises a computer, and a signal abnormity alarm module mounted on the computer; the detecting head comprises an emitter, an emitting wire and a receiver; the emitter emits ultrasonic signals to aroller to be detected by the emitting wire; the receiver is used for receiving the ultrasonic signals reflected by the roller to be detected and transmitting the reflected ultrasonic signals to the signal processing system; the signal processing system comprises a signal processor; the signal processor is used for processing the reflected ultrasonic signals and converting the processed signals toinformation capable of being identified by the computer to the computer; and the computer and the signal abnormity alarm module judge detecting conditions. The device directly generates one source ofself-excited vibration for a cold rolling mill, that is, local defects on the surface of the roller are detected and identified by using the ultrasonic signals without contacting with the rolling mill, so that the detecting and identifying accuracy is high, and production is not influenced.