After deterministic error compensation,various random noises become the main error sources of fiber optic gyro (FOG).To reduce the random errors of FOG,the denoising method based on wavelet packet filtering is studied,including the principle of wavelet packet filtering and the selection of threshold and thresholding operator,which is modified.The Allan variance method and power spectrum density (PSD) are adopted to analyze the random error characteristics before and after filtering,and the theoretical analysis of filtering effect can be realized.At last,simulation is carried out based on the drift data of FOG VG951,it is proved that the proposed method can decrease the random error of FOG effectively.