Abstract: For the forward-looking imaging of airborne platform, the platform motion will lead to range walk and Doppler ambiguity during the accumulation time. The Keystone transform can compensate the cross-range unit walk of the target during the forward-looking scanning time in the radar, however, in the case of Doppler ambiguity, the ambiguity number compensation of Keystone correction may introduce residual velocity and lead to target localization errors. We study the Keystone correction method for the forward-looking imaging of airborne platform and propose a method to compensate the residual range walk introduced by the Keystone transform, so as to improve the focus and accurate positioning of the target. The theoretical analysis and simulation experiments verify the effectiveness of the proposed algorithm.