A section of the single mode optical fiber stripping coated layer was discharged into two S-shape in a splicer at a distance of 25 mm and a Mach-Zehnder interferometer based on daul S-shape structure was formed. Part of the light can be excited into the cladding mode at the first S structure and return to the core mode at the second one. The S structure leads to the coupling between the core mode and the cladding mode and generates interference. Using the interference spectra to measure the response to external factors like temperature, refractive index, and micro displacement. Experimental results show that the sensitivities of temperature, refractive index and micro displacement are 69 pm/℃，132.64 nm/RIU，－178 pm/μm, respectively, and the measurement has a good linearity. The sensor has the merits of all-fiber structure, easy-fabricated and low-cost.