The TiO2 powders codoped by mole fraction x(Er3+)=0.1% Er3+ and x(Li+)=0-2% Li+ are prepared by the sol-gel method. The TiO2 phase transition from anatase to rutile is accelerated by Li+ codoping at the sintering temperature of 800 ℃,while only rutile phase existes at 900 ℃ and 1000 ℃. The green and red upconversion emissions centering at about 526,550 and 663 nm are detected by using a 976 nm semiconductor laser diode excitation. The two-photon absorption upconversion process is responsible for the green and red upconversion emissions. With the increase of the Li+ codoping concentration,the upconversion emissions intensities of Er3+-Li+:TiO2 sintered at 800 ℃ decreases,and that increases firstly and then decreases at 900 ℃,while the emission intensity increases significantly at 1000 ℃. The changes of crystal-field symmetry of Er3+ caused by Li+ codoping at different sintering temperature result in the variation of upconversion emission intensities of Er3+-Li+:TiO2. It is found that Li+ codoping can efficiently enhance the upconversion emission intensities of Er3+:TiO2.