The smear caused by a charge transfer for multi-phase TDI CCD in a remote sensing system couldn’t be eliminated by the motion compensation methods. First,the operation principle and forward motion compensation method are introduced. Then, according to the charge transfer mode of a TDI CCD,the velocity model of charge transfer in one line period is developed by employing an impulse function, velocities of image point and TDI CCD are analyzed, and why the charge transfer causes the smear is also presented. Furthermore,the Modulation Transfer Function of charge transfer smear existed in a multi phase TDI CCD is developed, and the contrasts of spatial frequency losses due to charge transfer smear for two, three and four phase TDI CCDs are illustrated. Finally, an image quality evaluation platform is established,an image drone with a resolution of 60 lp/mm is captured by a film aerial camera at Nyquist frequency, and effects of charge transfer smear on image quality for two, three and four phase TDI CCDs are studied,respectively. The results confirm that the proposed charge transfer model accords well with the experiment.