The invention relates to a switchable acousto-optic fiber orthomode transducer. A tunable light source is connected with a few-mode fiber via a single-mode fiber, and a mode stripper is connected withthe few-mode fiber. An RF generator is connected with an ultrasonic transducer to form an ultrasonic wave generating device, and a part of the coating layer is removed from the few-mode fiber, wherein this part of the few-mode fiber is vertically bonded with an emitting end of the ultrasonic transducer, and an outgoing end of the few-mode fiber is connected with an image capturing system. The tunable light source generates beams with different wavelengths, and the beams passes through the single-mode fiber to the few-mode fiber. The mode stripper in the few-mode fiber filters out a small number of high-order modes generated by the fusion in the fiber. The RF generator drives the ultrasonic transducer to generate ultrasonic waves, and the ultrasonic coupling enters into the few-mode fiberto form an acoustic-induced fiber grating. When the frequency of the RF generator is adjusted to meet a phase matching condition, the outgoing end of the few-mode fiber obtains the linearly polarizedmodes shown in the description. The few-mode fiber of the outgoing end is twisted and extruded to output +1 and -1-order vortex beams.