The output power and the signal-to-noise ratio of an overdamped harmonic oscillator are calculated in the case of square wave signal input. The corresponding stochastic resonance phenomenon and the comparison with the case of cosine signal input are discussed. Results reveal that there appear the stochastic resonances in these two cases, and the phenomenon in which the resonance and suppression are coexistent, but the coexistence phenomenon appears in the different stochastic resonance curves for these two models.