A rate equation model of multi-quantum wells vertical-cavity surface-emitting laser (VCSEL) is presented after theoretical analysis. The effects of photon density and the carrier capture-escape-tunnel time on the frequency response of VCSEL are simulated by the small signal analysis. The results both of simulation and experiment show that the modulation bandwidth of VCSEL is broadened with the power increasing. In addition, we simulate the small signal frequency response of the parasitic circuit of internal-contact oxide-confined VCSEL after analyzing its parasitic parameters.