Range and Doppler frequency cell migration induced by the movement of the low-observable target would bring about serious integration loss, which may deteriorate the target detection or imaging performance. Hence, this article proposes a migration correction algorithm based on keystone transform and modified generalized radon Fourier transform (KT-MGRFT). More specifically, KT is first utilized to eliminate the linear range cell migration (RCM) induced by the target unambiguous velocity. Then, MGRFT is presented to estimate the fold factor and acceleration. After that, the residual RCM and Doppler frequency cell migration (DFCM) are compensated by multiplying a reference signal constructed by the estimated fold factor and acceleration. Finally, the coherent integration can be achieved via the inverse Fourier transform (IFT) and the Fourier transform (FT) with respect to range frequency and scaled slow time, respectively. Compared with standard GRFT, the proposed method can remove the searching procedure of unambiguous velocity, and thus, it has lower computational complexity. In addition, through taking the maximum value in searching the range-Doppler frequency domain, the blind speed sidelobe (BSSL) effect is suppressed. Both the numerical simulations and the real experiment with the X-band radar are given to verify the effectiveness of the proposed method.