We address the recognition problem of velocity gate pull-off (VGPO) jamming from the target echo signal for the velocity automatic tracking system. To this end, we resort to the discrete chirp-Fourier transform (DCFT) to jointly estimate the chirp rates and frequencies of the target and jamming signals. Firstly, the scaling characteristic of the DCFT algorithm is explored. Then we highlight the quantitative effect of the VGPO jamming signal by analyzing the jointly estimated result in each pulse. The effective effect indicates that the relationship between the estimated chirp rate and the pulse is similar to that between the frequency offset of VGPO jamming and the time when the estimated frequency is unchanged. Finally, by utilizing the analytical result and extracting the feature of the mean square to variance ratio (MSVR) of the normalized estimated chirp rate, the VGPO jamming can be recognized. Simulation results show that, for a time when the estimated frequency is unchanged, the MSVR of VGPO jamming decreases with the pulse numbers increases, and is always larger than that of a target which is steady. Comparing to other methods, the proposed method can correctly recognize the jamming signal with jamming-to-noise ratio (JNR) 5dB which shows better recognition performance, and is also effective within a shorter period.