A novel method based on optical fiber sensors to realize the identification of characteristic frequency of Acoustic Emission (AE) signal is proposed. The system is structured by a ring optical fiber Sagnac interferometer which is used to detect the ultrasonic waves. The optical fiber sensor was fixed on the experimental material; press the experimental material with mechanical device, signals collected by a data acquisition circuit based on single chip were sent to the computer. The computer processed the signals further. The experimental results showed that the method using optical fiber sensors realized the identification of characteristic frequency of AE signal. This new method is useful for the structural health detecting and monitoring.