A series of Tm3+/Yb3+ co-doped oxyfluoride tellurite glasses with various Tm3+ concentrations was synthesized via a conventional high temperature solid state method. Absorption spectra showed that Yb3+ and Tm3+ were successfully incorporated into the matrix. The sample exhibited strong 801 nm emissions corresponding to 3H4→3H6 transitions, with weak 476 and 651 emission respectively corresponding to the 1G4→3H6 and 1G4→3F4 transition.Concentration dependence of up conversion luminescence was analyzed and it was found that the optimal Tm2O3 concentration for achieving maximum upconversion emission intensity was 0.1%.Up conversion luminescence mechanism and concentration quenching were studied by emission spectra. Tm3+ ions obtained energy mainly comes from the energy transfer from Yb3+ to Tm3+. The concentration quenching was attributed to the nonradiative energy transfer through cross relaxation mechanism due to dipole-dipole interaction between Tm3+. Based on this rule, the possible energy transfer processes can be1G4+3H6→3H5+3H4,1G4+3H6→3H4+3H5, 1G4+3H6→3F2,3+3F4 and 3H5+3H5→3H6+3F2. Additionally, the optical temperature sensing properties were investigated by using the thermal coupling 3F2,3 and 3H4 levels of Tm3+ under near infrared 980 nm excitation. The sample can be used as sensing material and better in high temperature sensitivity.