The threshold-array model is presented to study Suprathreshold Stochastic Resonance(SSR) phenomenon . Analysis of the model proves that that the threshold-array system can be decomposed into a cascade of a single threshold system and an ensemble averager. In order to study the Suprathreshold Stochastic Resonance with periodic input, the statistical properties of the output process of the threshold-array model is evaluated. With a fixed input signal-to-noise ratio, the output SNR Gain of the model varies in a non-monotonic way when injecting independent threshold noises into the array. If the input noise is Gaussian, when adding independent Gaussian white threshold noises into the array, a SNR Gain larger than unity can be obtained. Moreover, when the input noise is non-Gaussian, there will be a better SNR Gain.