An optical fiber microdisplacement sensor based on symmetric Mach-Zehnder interferometer (MZI) with a seven-core fiber and two single-mode fiber balls is proposed. The rationality and manufacturing process of the MZI sensing structure are analyzed. The fabrication mechanism of the Mach-Zehnder sensor by CO2 laser is described in detail. Experimental results show that temperature sensitivities of the two dips are 98.65pm/℃ and 89.72pm/℃, respectively. The microdisplacement sensitivities are 2017.71 pm/mm and 2457.92 pm/mm, respectively. The simultaneous measurement of temperature and microdisplacement is demonstrated based on the sensitive matrix. The proposed Mach-Zehnder interference sensor exhibits the advantages of compact structure, simple manufacturing process, and high reliability.