Photon-generated carrier of ferroelectric photovoltaic effect is different from the carrier of traditional photovoltaic effect, which makes the ferroelectric photovoltaic effect much more excellent. It is of great significance to improve the photoelectric conversion efficiency, and overcome the shortcoming of large band gap of ferroelectric thin film, which has been an important subject of research in ferroelectric photovoltaic effect. In this work, BTO ferroelectric thin films with different doping concentration of Fe were prepared by sol-gel method to reduce the optical band gap. In order to study impact of different Fe doping concentration on photovoltaic effect of ferroelectric thin film, the film composition, microstructure, band gap and other factors were characterized. Research result shows that the doped Fe with concentration of (Bi4Ti3-xFexO12) changing from x = 0.8 to x = 1.2 does not transform the matrix structure of BTO; The doped film has good crystallinity, obvious reticular structure, well-proportioned spatial distribution and uniform grain size. The Fe-BTO ferroelectric thin films prepared by sol-gel method can significantly tune its band gap.