We investigate the pump-depleted model of a dual-pump fiber optical parametric amplifier (FOPA) with Raman effect. As bandwidth increases, the gain profile of the distorted FOPA would be impacted seriously. Under the widebands, especially when the pump separation is large, zero dispersion wavelength (ZDW) fluctuation is another factor which can not be neglected. Numerical simulations with these comprehensive factors are mainly analyzed to obtain their influence on gain characteristics. Saturated gain spectrum is also discussed in detail.