A compact optical fiber sensor based on a Mach-Zehnder interferometer embedded in fiber Bragg grating was proposed and experimentally demonstrated. The Mach-Zehnder interferometer is realized by concatenating two spherical-shape structures separated by a middle section. The spherical-shape structures act as a mode splitter and a mode collector,respectively. The effects of different structure parameters of Mach-Zehnder interferometer were discussed. As a result,the resonant wavelength of the fiber Bragg grating and the interference dip of the Mach-Zehnder interferometer have the different sensitivities of temperature,refractive index and liquid level. Experiment results show that the sensitivities of interference dip of Mach-Zehnder interferometer to temperature,refractive and liquid level are 0.072 4 nm/℃,87.65 nm/RIU and －0.029 714 nm/mm,respectively,the resonant wavelength of the fiber Bragg grating has sensitivity of 0.009 89 nm/℃ to temperature,while is insensitive to refractive index and liquid level. The simultaneous measurement of dual parameters can be realized by sensitive matrix. This kind of sensor will have wild applications in chemistry,biology and pharmacy.