Abstract: For the motion estimation problems of image super-resolution，a two-step estimation method is proposed to estimate relative motion parameters between low-resolution images.Firstly，a certain method such as correlation-or distance-based method is used to estimate integer-pixels shift parameters between two images，one of them is then compensated to aligne to another.Secondly，the gradient-based method is used for the aligned images to estimate fraction-pixels shift parameters between them.Through the two estimation step，the accurate motion parameter is obtained at high speed without interpolating the low resolution images.