Two series of Tm3+ and Yb3+codoped oxy-fluorosilicate glass ceramics with the composition of 30SiO2-(20-x-y)Al2O3-40PbF2-10CdF2-xTm2O3-yYb2O3 were prepared and characterized. The up-conversion spectra of the samples were investigated and the up-conversion luminescence mechanisms of Tm3+/Yb3+ system were analyzed. The effects of Tm3+ and Yb3+ concentration on up-conversion luminescence spectra weresystematically studied. The results suggest that blue up-conversion emission intensity decreases when Tm3+ concentration increases due to the cross relaxation interaction between Tm3+ ions. The optimum Tm3+ concentration is 0.025mol%. Three-photon process and Yb3+ ion cooperative up-conversion energy transfer process co-exist in the Tm3+/Yb3+ up-conversion luminescence system. When Yb3+ concentration increases, due to the energy back-transfer process of 3H4(Tm3+)→2F5/2(Yb3+), the blue up-conversion emission intensity would decrease. With the help of Yb3+ ion cooperative up-conversion energy transfer, the blue up-conversion emission intensity actually increases, which is in accordance with the experimental results.