The Er3+, Yb3+-doped CaO-Y2O3-Al2O3-SiO2 glasses were prepared by melting, and then annealed. The emission spectra and upconversion spectra of glass-ceramics have been investigated. The upconversion luminescence mechanisms of Er3+ in YAG glass-ceramics were analyzed. The results show that the Er,Yb:YAG glass-ceramics are obtained after annealing of the glasses. A broad emission spectrum of width 200nm in the wavelength range of 1450—1650nm was obtained in Er,Yb:YAG glass-ceramics at room temperature. The full width at half-maximum (FWHM) of the 4I13/2→4I15/2 transition is ～180nm. This may be as a result of the luminescence of the Er3+ ions in YAG crystal phase and the remnant Er3+ ions in glass phase acting together. The upconversion luminescence intensity increases because the phonon energy of YAG crystallite is lower than that of aluminosilicate glass. The infrared to green or to red upconversion luminescence intensities for the glass-ceramics are evaluated to be nearly 7 or 3 times as high as that of aluminosilicate glasses, respectively. The relative intensities of green and red upconversion emission changed because the microscopic environment around Er3+ and Yb3+ ions changed upon heat treatment.