A new piecewise-linear stochastic resonance model was proposed in this paper. Using numerical simulation, the model was compared with nonlinear one-dimensional continuous bi-stable system on response to period signals under both noisy and non-noisy circumstances. Comparing with contrasting model, there is no output response saturation phenomenon, and the output will increase greatly with the increasing of input signal. To input signal with noise, there is larger applicability to noise intense, especially to weak signal with large additive noise, still there is stochastic resonance. It is superior to contrasting model.