The invention discloses an acoustic emission sensor, comprising a double-clad optical fiber, a single-mode input optical fiber and a single-mode output optical fiber, wherein the single-mode input optical fiber and the single-mode output optical fiber are connected at two ends of the double-clad optical fiber respectively through an optical path, a silicone rubber coating sensitive to an acoustic emission vibration is cladded outside the double-clad optical fiber, an external acoustic emission vibration can enable a deformation of the silicone rubber coating, a dynamic phase variation is introduced for a cladding mode of the double-clad optical fiber, and acoustic emission parameters are sensed by detecting resonant filtering characteristics. The acoustic emission sensor disclosed by the invention is an all-fiber structure, and has the advantages of compact structure, simple manufacturing method and convenience for use, and the double-clad optical fiber and the single-mode optical fibers can be directly fusion-welded with each other by means of conventional welding equipment.