Abstract: A phase-sensitive optical time domain reflectometer(-OTDR) and Mach-Zehnder interferometer based fiber-optic distributed disturbance sensor was proposed in this paper. The aim is to obtain a low false alarm rate compared with current single -OTDR, which suffers from the high false rate due to the instability of scattering light intensity fluctuation in -OTDR. In the proposed sensor, -OTDR and Mach-Zehnder interferometer were multiplexed together. So, the -OTDR was used to detect and locate the disturbance, and the Mach-Zehnder interferometer was utilized to detect the disturbance, respectively. Then, the disturbance detected by -OTDR can be confirmed by the M-Z interferometer to realize a low false alarm rate due to the instability of -OTDR. The feasibility and effectivity of the proposed method by multiplexed -OTDR and Mach-Zehnder interferometer were validated in experiment, by comparing with current single -OTDR. It is found that the false alarm rate can be reduced to 2% from 25% by the single -OTDR.