A new simulation model of the Josephson junction array coupled with a Fabry-Perot resonator is presented in this paper, which considered the excitation of the resonance mode by the array and the influence of the resonance mode on the array. Taking advantage of the new model, we investigate the phase-locking properties of the junctions. The results include the influence of the Q value of the resonator, the strength of the coupling between the junctions and the resonator as well as the number of junctions in the array on the phase locking properties. It is useful in the detection of THz signal and fabrication of THz sources using Josephson junction arrays.