Abstract: In this paper, the signal model of airborne SAR moving target echo is constructed firstly, which is a chirp signal naturally. According to this feature, a new technique of SAR moving target detection based on fractional Fourier transform is proposed. The effects of coupling in time-frequency domain on signal detection are eliminated. Compare with the bilinear time-frequency distribution algorithms, the fractional Fourier transform is a linear operator, and it will not affected by the intercross terms when multiple moving targets exist. The simulation results validate the effectiveness of this technique.