The eigen frequency is a key parameter of a fiber optic gyroscope (FOG). We present an online eigen frequency tracking method for FOG technology based on the staircase waveform and a four-step frequency perturbation. Results show that the measurement accuracy of the eigen frequency does not exceed 1.7 Hz for a temperature range of 27.5°C-62.5°C and a variation rate of 0.24°C/min. This is in good agreement with the theoretical model. The method, which exhibits a low time-space complexity, simply requires the addition of a low-rate digital-to-analog converter to the existing gyro system. There is no requirement for the type of staircase waveform in the phase modulation, and the staircase waveform remains unchanged. Thus, this method can be easily transplanted into other algorithms.