Abstract: The distributed optical fiber positioning system in coal mine usually adopts the dual Mach-Zehnder interferometer distributed optical fiber vibration sensing technology． The sensing distance is short and the spatial resolution of the system is not high． A distributed optical fiber vibration sensing technique for asymmetric double Mach-Zehnder interferometer is proposed． It uses two DFB ( Distributed Feedback) laser beams and DWDM( Dense Wavelength Division Multiplexing ) ， the noise reduction is processed by SVD ( Singular Value Decomposition) algorithm，and a cross-correlation delay algorithm based on SVD is proposed． Experiments show that the localization method can effectively improve positioning accuracy and sensing distance． When the sensing distance is 61 km，the positioning error is 51． 2 m． When the mine disaster happens，it can locate the trapped people accurately，and guarantee the effective rescue time．

Key words: coal mine, distributed optical fiber vibration sensing technology, asymmetric double Mach-Zehnder interferometer, singular value decomposition ( SVD) algorithm, underground positioning