The absorption spectrum, upconversion spectra and Raman spectrum of Er3+/Yb3+-codoped oxyfluorosilicate glasses have been investigated, and upconversion luminescence mechanisms of Yb3+ sensitize Er3+ in oxyfluorosilicate glasses were analyzed. The results showed that blue, green and red emission centered around 408 nm, 529 nm, 545 nm, and 667 nm, corresponding to the 2H9/2→4I15/2,2H11/2→4I15/2,4S3/2→4I15/2, and 4F9/2→4I15/2 transitions of Er3+, respectively, were simultaneously observed at room temperature under 975 nm diode laser excitation, and the intensity for blue, green and red emissions increases with the increasing Yb2O3 concentrations because energy transfer from Yb3+ to Er3+ was reinforced. A two-photon upconversion process is assigned to the intense green and red emission, respectively, while a three-photon process is responsible for weak blue upconversion. Raman spectrum indicates that the lead fluoride in the glass network play an important part in upconversion fluorescence of Er3+.