Aiming at the nonlinear electro-optical response in the Mach-Zehnder Interferometer (MZI)-based silicon modulator, the model with the nonlinear modulating loss in PN junction and the nonlinear refractive index changing was utilized, and the influence of modulating loss on the silicon modulator was investigated for two cases: symmetric arm or asymmetric arm in the MZI-based modulator. By taking account of the modulating loss in the model, the results can be obtained that in the condition of large signal, the third order harmonic component is enhanced and the fourth order harmonic component is reduced when the bias phase of the optical modulator is 0, and the second order and fourth order harmonic component are all enhanced when the bias phase of the optical modulator is π/2. While in the condition of small signal, the high order harmonic components, such as the third order and fourth order harmonic components, are not obvious, and the crosstalk of fundamental frequency is enhanced by the modulating loss when the bias phase of the optical modulator is 0 and two arms in the modulator are asymmetric, the second order harmonic component is enhanced by the modulating loss when the bias phase of the optical modulator is π/2.