We propose a novel Mach-Zehnder interferometer (MZI) type thermo-optic switch based on SU8-silica hybrid waveguide structures. The switch consists of a 1 × 2 power splitter, two transmission arms and a 2 × 1 power combiner. The input/output waveguides and the power splitter/combiner are realized by the conventional silica waveguides, while the two arms for the MZI consist of SU8 strip waveguides. Such hybrid SU8-Silica waveguide strucutures combines the advantages of the low propagation loss of the silica waveguides and the large thermo-optic coefficient of SU8. Due to the high thermo-optic coefficient of SU8, the length of the transmission arm can be dramatically reduced.