For synthetic aperture radar (SAR), ground moving target (GMT) imaging necessitates the compensation of the additional azimuth modulation contributed by the unknown movement of the GMT. That is to say, it is necessary to estimate the Doppler parameters of the GMT without a priori knowledge of the GMT’s motion parameters. This paper presents a Doppler parameter and velocity estimation method to refocus the GMT from its smeared response in SAR image. The main idea of this method is that an azimuth reference function is constructed to do the correlation integral with the azimuth signal of the GMT. And in general, the Doppler parameters of the presumed azimuth reference function are different from those of the GMT’s azimuth signal since the velocity parameters of the GMT are unknown. Therefore, the correlation operation referred to here is actually mismatched, and the processing result of is shifted and defocused. The shifted and defocused result is utilized to get the real Doppler parameters and the velocity parameters of the GMT. One advantage of this method is that it is a nonsearching method. Another advantage is that both the Doppler centroid and the Doppler frequency rate of the GMT can be simultaneously estimated according to the relationships between the Doppler parameters and the smeared response of the GMT. In addition, the velocity of the GMT can also be obtained based on the estimated Doppler parameters. Numerical simulations and experimental data processing verify the validity of the method proposed.