Abstract: H.264 is the latest international video coding standard，it supports high accurate subpel motion estimation.When the fast integer motion estimation is used，the computational load of subpel motion estimation may be the bottleneck of motion estimation.According to the monotonically increasing match criteria around the location of the optimal motion vector a fast fractional motion estimation algorithm based on the group error is presented.Simulation results show that it can save the search points of subpel motion estimation efficiently with very low rate distortion loss.