A polarization-maintaining fully-reciprocal bi-directional optical carrier microwave resonance system and an angular velocity measurement method thereof. In the system, highly stable optical carrier microwaves are generated in a clockwise direction and a counterclockwise direction in the same resonant cavity, and are used to measure the angular velocity of rotation of a carrier apparatus. A fully reciprocal ring-shaped resonant cavity structure is used to achieve a fully reciprocal bi-directional optical resonance system. A polarization state separation technique is used to separate an optical signal into two wavelengths, and optical signals with perpendicular polarization states are transmitted in opposite directions in a sensing ring, thereby improving the measurement capability of the sensing ring. Bi-directional optical carrier microwave resonance is achieved by using a phase tracking structure and a regenerative mode locking technique. A cavity length control technique is used to lock the oscillation frequency of microwaves in one of the directions to a highly stable standard time reference source, thereby achieving a stable relative cavity length of an optical resonant cavity. The described key techniques greatly improve the signal-to-noise ratio of bi-directional oscillation difference frequency signals caused by the Sagnac effect. The system and the method are practical and have high measurement precision.