The effect of annealing pressure on the structure and ferroelectric properties was investigated for Bi3.25La0.75Ti3O12(BLT) thin film prepared on Pt/TiO2/SiO2/p-Si(100) substrate by sol-gel method. The amorphous film samples were annealed at 750 ℃ for 30 min under oxygen pressures varying from 10-4 to 3 atm. Then the structure, crystallization degree, and morphology were characterized by X-ray diffraction (XRD), Raman spectroscopy, and field-emission scanning electron microscope (FSEM) to clarify the effect of annealing pressure on the structure of the film. The XRD and Raman spectroscopy results showed a clear decreasing of the crystallization degree of the film annealed under oxygen pressures of 10-4 and 3 atm. FSEM results showed different growth orientations of grains under different oxygen pressures. The structure of the BLT film was revealed to affect their ferroelectric properties. The largest remanent polarization of 17.8 μC/cm2 with the coercive field of 73.6 kV/cm and good fatigue property were obtained for the film annealed under oxygen pressure of 0.1 atm.