The plasma surface wave propagation in a rectangular structured device is simulated using the finite-difference time-domain method. The effect of device parameters on the propagation of plasma surface wave excited by slot antenna array is investigated. The parameters considered include the relative permittivity and thickness of dielectric slab, and the air gap on the top of dielectric slab. Appropriate parameters for the relative permittivity and thickness of dielectric slab are obtained through simulations, and it is found that the existence of air gap would greatly weaken the excitation of surface wave. The simulation results provide a good reference for the design optimization of large-scale rectangular surface-wave plasma source.