Abstract: A novel mechanism of surface plasmon polaritons (SPPs) electron beam excitation is presented in this paper. The mimicking surface plasmon polaritons (MSPPs) on the nano-slits array excited by parallel moving electron beam are used to couple coherent and tunable SPPs on the metal surface. The results of numerical calculations and particle-in-cell simulations show that it brings many significant advantages to SPPs excitation. Based on this mechanism, SPPs can be coupled efficiently, regardless of the distance between the metal surface and the electron beam. The decay time of the coupled SPPs is as long as that of the excited MSPPs, and the amplitudes of the coupled SPPs are two orders of magnitude larger than that of SPPs excited by electron beam directly. Accordingly, this mechanism may bring great significances for the applications of SPPs.