The invention discloses a polarization-state-controlled multimode-interference optical switch. The polarization-state-controlled multimode-interference optical switch comprises a planar optical wave and optical path chip, a light source, a polarization controller and an input fiber array. The planar optical wave and optical path chip comprises a silicon substrate, a silica buffer layer, waveguides and a covering layer. Cracks are formed in the silica buffer layer. The waveguides comprise an input-stage single-mode waveguide, an intermediate-stage multimode waveguide and an output-stage single-mode waveguide. The light source is connected with the optical input end of the polarization controller, and the optical output end of the polarization controller is connected with the input end of the input fiber array. The switch-on/off state of the multimode-interference optical switch is adjustable, and the multimode-interference optical switch has the advantages of thermal stabilization, low nonlinearity, low transmission loss, wide operation bandwidth and high integration and being capable of being efficiently coupled with a single-mode fiber, low in price, simple in structure, and the like. Meanwhile, the invention further discloses a manufacturing method of the polarization-state-controlled multimode-interference optical switch. The manufacturing method is simple, low in cost and capable of manufacturing the optical switch in batches.