Estimating cross-range velocity is a challenging task for space-borne synthetic aperture radar (SAR), which is important for ground moving target indication (GMTI). Because the velocity of a target is very small compared with that of the satellite, it is difficult to correctly estimate it using a conventional monostatic platform algorithm. To overcome this problem, a novel method employing multistatic SAR is presented in this letter. The proposed hybrid method, which is based on an extended space-time model (ESTIM) of the azimuth signal, has two steps: first, a set of finite impulse response (FIR) filter banks based on a fractional Fourier transform (FrFT) is used to separate multiple targets within a range gate; second, a cross-correlation spectrum weighted subspace fitting (CSWSF) algorithm is applied to each of the separated signals in order to estimate their respective parameters. As verified through computer simulation with the constellations of Cartwheel, Pendulum and Helix, this proposed time-frequency-subspace method effectively improves the estimation precision of the cross-range velocities of multiple targets.