High　speed　optical　switches　are　critical　components　in　the　realization　of　light　transmission　path　switching　technology　for　optical　networks.　Current　Mach-Zehnder　Interferometer　type　optical　switches　either　occupy　larger　footprint　or　have　a　longer　one-dimensional　scale.　A　Silicon-based　rectangular　Mach-Zehnder　2×2　thermo-optical　switch　unit　is　proposed　for　the　highly　integrated　applications.　The　novel　optical　switch　consists　of　trench-based　nanophotonic　frustrated　total　internal　reflection　couplers　and　total　internal　reflection　mirror-based　90°　waveguide　bends.　The　switching　operation　is　achieved　through　thermo-optical　effect　of　Silicon.　As　a　design　example,　the　~84　μm　long　L-shape　phase-shifting　arm　is　determined　for　π　phase　shift　when　its　temperature　of　the　arm　is　increased　up　to　50°C.　A　switching　voltage　of　3.5　V　on　a　NiCr　metal　electrode　heater　is　obtained　by　using　finite　element　method.　The　voltage　may　lead　to　the　increase　of　50°C　for　an　optical　ridge　waveguide　in　the　L-shape　phase-shifting　arm.　The　time　response　of　the　device　is　simulated　as　a　function　of　different　upper　dielectric　thickness　of　SiO2,　and　the　response　time　including　raise　time　of　35　μs　and　fall　time　of　48　μs　is　optimized　for　the　device　with　0.5　μm　thickness　of　upper　SiO2.　The　switching　function　of　the　thermo-optical　switch　is　simulated　and　verified　by　Rsoft　FullWAVE　software,　a　finite　difference　time　domain　method.　The　chip　size　of　56×38　μm2　is　designed　for　the　Silicon-based　rectangular　Mach-Zehnder　2×2　optical　switch.　The　device　is　ultra-compact,　and　its　configuration　is　beneficial　to　extend　at　two-dimensional　directions,　making　them　attractive　for　Silicon-based　high　dense　photonic　integrated　circuits　and　on-chip　optical　interconnect　system.