Er3+:Y2O3 nanocrystals codoping with Li+ are prepared by glycine combustion method. The samples are characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and photoluminescent measurements. Effect of the Li+ molar fraction on the structure and the fluorescence intensity of the nanocrystals are investigated. The XRD result indicates good crystallinity. The luminescent test results show that with the increase of the Li+ codoping fraction, the fluorescence intensity of the nanocrystals around 1.5 μm enhances remarkably. The luminous efficiency of Er3+ is increased by codoping Li+, which can modify the lattice symmetry of the nanocrystals.