A　1x4　LiNbO3　electro-optic　switch　is　proposed　based　on　Mach-Zehnder　interference　structure.　The　optical　switch　is　composed　of　three　1x2　MZI　switch　units,　each　of　which　includes　Y　branch,　interference　arm　and　directional　coupler.　The　phase　difference　of　the　light　propagating　on　two　interference　arms　is　generated　through　the　loaded　bias　voltage,　and　the　switching　between　the　two　output　ports　of　the　MZI　switch　unit　can　be　realized.　The　parameters　of　Y　branch　and　directional　coupler　of　optical　switch　are　designed　and　optimized,　and　the　performance　of　the　whole　device　is　simulated.　The　total　length　of　the　device　is　5.8cm　and　the　insertion　loss　is　0.54dB.　The　extinction　ratio　bandwidth　larger　than　20dB　reaches　100nm,　and　the　maximum　extinction　ratio　at　the　wavelength　of　1550nm　is　33dB.　The　function　of　optical　switch　with　four-channel　gating　is　realized.　The　proposed　optical　switch　is　expected　to　be　used　in　the　fields　of　optical　interconnection　and　optical　signal　monitoring　on　high-speed　integrated　chips.