Based on the silicon dioxide planar waveguide platform, a low power thermo-optical switch with multi-mode interference Mach-Zender is designed and fabricated. This device combines the stability of multi-mode interference coupler with the advantages of silicon dioxide waveguide and thermo-optical switch. The device parameters are optimized by simulation and the influence of the distance between the metal layer and the waveguide on the transmitted light intensity and power consumption is discussed. The test results show that the device has stable structure, small polarization dependence, insertion loss less than 2 dB. It can realize switch conversion. The power consumption is about 450 mW. The switching response time is 103 μs and 113 μs. The extinction ratio is more than 16 dB at 1 564 nm wavelength, and the size is 2.3 cm×0.25 mm. The device is not only compatible with CMOS technology, but also has good compatibility with optical fiber. Due to the advantages of low cost, large output and stable performance, the silicon dioxide waveguide optical switching devices provide a solid foundation for the development of optical communication and optical computing in the future.