The 0.1%～3.0% Er3+-doped TiO2 nanocrystals have been prepared by sol-gel method in which titanium etrachloride was adopted as the precursor. The phase structure, composition and phonon cutoff energy of Er3+-doped TiO2 nanocrystals were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectra and Raman spectra. The nanocrystalline size of TiO2 is reduced with increasing Er3+ concentration. The intense green and red emissions around 525 nm, 548 nm and 660 nm corresponding to the 2H11/2→4I15/2,4S3/2→4I15/2 and 4F9/2→4I15/2 transition of Er3+ ions were observed under excitation by 980 nm. The relations among Er3+ concentration, the heat treatment temperature, laser power and upconverted emissions were studied. The result indicated that in the sample, when the Er3+ concentration is 0.5%, the heat treatment temperature is 800 ℃, the upconversion luminous efficiency is highest .The upconversion mechanisms of Er3+-doped TiO2 nanocrystals were also discussed.