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.