A polymeric Mach- Zehnder interferometer (MZI) thermo- optic (TO) switch with low power consumption is designed and fabricated. The polymer materials have the advantages of low thermal conductivity and high thermo-optic coefficient. Therefore it can reduce the power consumption of the thermooptic device effectively. The TO switch is designed on the SiO2 substrate with selecting the Norland optical adhesive (NOA73) as the core layer and using Poly (methyl methacrylate- glycidyl methacrylate) [P(MMAGMA)] as the upper cladding. The light field and thermal field distribution of the TO switch are both simulated. The TO switch is fabricated by using the traditional semiconductor technology. At 1550 nm wavelength, the extinction ratio of the device is 20.2 dB and the power consumption is only about 9.14 mW. The rise time and the fall time of the switch are 174 ms and 292 ms, respectively.