Nano-TiO2 modified by ionic liquid was prepared by sol-gel method with Ti(OC4H9)4 as titanium source. The chemical structure of the nanopartical was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and UV-Vis diffuse reflectance spectra (UV-Vis DRS). The results indicated that the modified TiO2 was almost entirely small nanocrystal and multihole and had high crystallinity. Radius of the modified particals had some degeree of reduction than that of the pure TiO2. The optical absorptivity of modified TiO2 is stronger than that of unmodified TiO2. The photocatalytic degradation activity of methylene blue with the prepared TiO2 was investigated. The degradation rate could reach more than 88%.