In this paper, we present a broadband, high-extinction-ratio, nonvolatile 2×2 Mach-Zehnder interferometer (MZI) optical switch based on the phase change material Sb2Se3. The insertion loss (IL) is 0.84 dB and the extinction ratio (ER) reaches 28.8 dB at the wavelength of 1550 nm. The 3 dB bandwidth is greater than 150 nm. Within the 3 dB bandwidth, the ER is greater than 20.3 dB and 16.3 dB at bar and cross states, respectively. The power consumption for crystallization and amorphization of Sb2Se3 is 105.86 nJ and 49 nJ, respectively. The switch holds significant promise for optical interconnects and optical computing applications.