In order to eliminate the interference of airborne environment and to improve the precision of decode and the EMC ability, the filtering of IRIG-B (AC) and the compensation of phase hysteresis caused by the filter are studied. A band-pass filter with a 1 kHz center frequency is designed, then the digital compensation is used for the phase hysteresis caused by filter. The results show that the ability of anti-jamming, anti-distortion and the decoding stability of the decoder are improved,and the useless frequency signals are depressed by -34 dB/10 octave. The digital compensation strategy can eliminate not only the phase hysteresis, but also the error caused by zero-crossing detector. The timing precision of 1 PPS is enhanced from better than 10 μs to better than 3 μs.The airborne system satisfies the decoding requirement of IRIG-B (AC), eliminates the noise interference and signal distortion,and enhances the decoding precision and stability.