A type of acousto-optic gyroscope based on polarization-mode conversion is presented, the principle and structure is analyzed and some tests of the gyroscope are carried out. The sensitivity of sensor is also given. The statical result shows that the coupling efficient is 80.02% when the length of acousto-optic interaction is 15 mm, the input electrical power of surface acoustic wave (SAW) is 100 mW and the frequency of SAW is 168.201 MHz. A linear voltage-rotation response curve of the gyroscope is obtained when rotating, and the sensitivity is 1 mV/[(°)/s]. Acousto-optic gyroscope based on polarization-mode conversion keeps the advantage of SAW gyroscope, and the sensitivity is enhanced greatly.