Abstarct: Bismuth ferrite (BiFeO3) is a well-known multi-ferroic having both ferroelectric and antiferromagnetic properties at room trmperature. BiFeO3 has orthorhombic perovskite structure with R3c space group. In this thesis, we study the structural, optical and electrical properties of BiFeO3 (BFO) thin films prepared by the sol-gel method on glass and FTO substrates. X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), and optical spectroscopy (UV-Vis) were used to characterize the samples. The structural properties of the films synthesized by using acetic acid and 2-methoxyethanol, confirmed formation of the orthorhombic phase. Examination of the optical properties of the samples showed that the band gap values of the samples are in the range of 2.06-2.38 eV. Investigation of pH effects revealed the transparency of the films improved with increasing pHbut there was no change in the band gap of the films. The band gap value of the sample prepared with higher pH value and annealed at 500 °C for 1 hour reduced from 2.94 to 2.43 eV. The effect of annealing temperatures was also investigated and the result confirmed the formation of BiFeO3 phase, but a little secondary phase were also observed in the samples, which decreased with increasing temperature from 500 to 600 °C and then increased from 600 to 700 °C. According to the morphological study of the surface of the samples, the crystallinity of the samples improved with increasing temperature. To reduce the secondary phases, the sample annealed at 500 °C at vacuum atmosphere but no effect was observed on removing the secondary phases. The electrical properties were also studied but the optical response was very low. So a sample with a thickness of about 400 nm was synthesized and the result indicated improvement of the optical response.