The utility model relates to a resonator fiber optic gyro with high sensitivity, belonging to the technical field of a fiber optic gyro, which aims at overcoming the problems that low sensibility (0.1 degree / hour) exists upon prior resonator fiber optic gyro and can not meet attitude tracking of short range / midrange missiles and commercial aircrafts, more particularly can not meet areas such as space positioning and submarine navigation with high requirement for sensibility. The utility model is characterized in that a laser output end of a frequency conversion laser (1) is connected with a dispersion fiber ring resonator (11) through a group speed control system (2), a fiber beam splitter (3), a first lithium niobate phase modulator (4), a second lithium niobate phase modulator (5), a first optical fiber coupler (6), a second optical fiber coupler (7) and a third optical fiber coupler (10). The utility model has the advantages of high sensibility up to ng times (The ng is group speed refractive index), low production cost, simple structure and small size.