The invention discloses a high-precision annular oscillator, and a frequency calibration circuit and method thereof. The high-precision annular oscillator comprises a band gap reference circuit, a reference current circuit, a current adjusting circuit, an annular oscillation circuit and an output buffer circuit. The frequency calibration circuit comprises a frequency divider, a counter, a comparator, a register and a nonvolatile memory. The frequency calibration circuit can rapidly position the adjusting current needed by the high-precision annular oscillator and store an adjustment arrangement in the nonvolatile memory. According to the invention, the high-precision annular oscillator cooperates with the frequency calibration circuit so that the effects of temperature deviations, voltage deviations and technology deviations on oscillation frequencies can be compensated, and thus the high precision of the oscillation frequencies can be realized. Through the cooperation between the high-precision annular oscillator and the frequency calibration circuit, high-precision oscillation frequencies are obtained, at the same time a complex circuit is avoided, the area and power consumption of a chip are reduced, the non-linearity, error and noise of a simulation comparison circuit are avoided, the frequency precision is improved, and the testing time and cost of the chip are saved.