The invention discloses an acoustic sensitization optical fiber based on cladding softening and multi-cladding structure, and relates to the technical field of sensing optical fibers. The invention comprises an optical fiber core and a cladding structure for wrapping the optical fiber core, wherein the outer surface of the cladding structure is coated with an optical fiber coating layer, and the optical fiber cladding structure is doped and softened or coated with a soft package layer material, so that the Young modulus of the optical fiber cladding structure is smaller than that of the optical fiber core. When external sound wave pressure acts on the optical fiber, the outer cladding with smaller Young modulus drives the inner cladding with larger Young modulus and the fiber core to deform, so that the response sensitivity of the optical fiber to sound waves is enhanced. The invention has the advantages of being simple in structure and capable of remarkably improving the strain-phasesensitivity of the optical fiber distributed acoustic wave sensing system.