A novel double Sagnac distributed fiber-optic sensor based on Sagnac interferometer for determining the position of disturbance along an optical fiber is presented. The configuration and operating principle of the system are illustrated,and the location principle and method for the detection system are analyzed. The system realizes the location of disturbances by using the adaptive time-delay estimation with the least mean square (LMS) algorithm in the time domain. Theoretical analysis and experimental results show that the proposed technology can realize the detection and location of the disturbed signal rapidly and effectively. This method is simple and can be obtained easily,and it has high measurement sensitivity and location precision. The maximm location error is less than 20 m.