In the present paper, we propose an effective method to enhance the intensity of the harmonic spectrum by using the He+ ion chain model. Through solving the time-dependent Schr?dinger equation, the harmonic spectra from the single He+ ion and the He+ ion chain have been theoretically calculated. Moreover, the ionization probabilities, the time-frequency analyses of the harmonic spectra and the time dependent wave functions have been used to explain the harmonic emission process and the electron motion. Results show that the harmonic intensity can be remarkably enhanced and the harmonic cutoff can be extended.
