In order to improve the phase carrier demodulation effect of aperiodic low frequency dynamic signal of optical fiber sensor , the phase carrier demodulation method of aperiodic low frequency dynamic signal of optical fiber sensor is proposed. Adaptive beamforming algorithm is used to enhance the details of aperiodic low-frequency dynamic signals ; The signal features are extracted by singular value decomposition algorithm; The extracted features are input into the CD3S signal demodulation model based on the double extended Kalman filter , and the noise is eliminated through the Kalman filter structure ; Through joint estimation , the spread spectrum code synchronization of the dynamic signal is realized , and the phase carrier demodulation of the aperiodic low-frequency dynamic signal of the optical fiber sensor is completed. The experimental results show that the demodulation error rate of the proposed method is below 1. 0% with or without noise interference , and the displacement error after demodulation is as low as 12 pm , which im- proves the demodulation effect and anti-noise ability.