For single-integrator kinematics of multi-agent systems with directed graph topology, the fast group consensus problem both in the situations of unknown and known state difference value is studied.A fast consensus protocol based on memory states is proposed.Based on the matrix theory and frequency-domain analysis, the sufficient conditions for system group convergence under two situations are provided respectively.Moreover, the upper bounds of time of memory states are provided respectively to increase the convergence speed of the multi-agent systems.Simulation results show the effectiveness of the proposed protocol．