A new model of stochastic resonance, in which the pulse signal is modulated by noise, is established for a single-mode laser system. The corresponding intensity correlation function and the output signal-to-noise ratio of the system are calculated in the linear approximation. The phenomena of stochastic resonance are thoroughly discussed. Results reveal that due to the pulse signal modulated by noise, the single-mode laser exhibits a novel stochastic resonance phenomenon, that is, the optimization or the restraint of output signal-to-noise ratio can be controlled by the adjustment of the pulse signal period T.