The novel zero-path-difference interferometer,of which the annular fiber arm of Sagnac interferometer is converted into linear structure by using a Faraday rotator mirror(FRM),can overcome the shortcoming of traditional optical fiber Sagnac interferometer.Moreover,FRM being used as a polarization compensator eliminates the problem of the polarization-induced signal fading.This device was analyzed in theory and sound field leakage of pipeline was studied as an example in experiment.The experimental result accords with the theoretic analysis and the location inaccuracy is less than 1 %,which shows that the novel device can realize the detection and location of the wideband sound signal source.