Novel transparent glass-ceramics containing Ag@NaGdF4:Er3+ core-shell nanocrystals were fabricated successfully by a melt-quenching method and subsequent heating. X-ray diffraction and transmission electron microscope images show that precious metal Ag is successfully encapsulated by the NaGdF4:Er(3+ )nanoparticles to form an Ag@NaGdF4:Er3+ core-shell structure in glass matrix. Compared with the NaGdF4:Er3+ glass-ceramics, Ag@NaGdF4:Er3+ core-shell glass-ceramics shows the great enhancement of emission intensity. The thermometric parameters such as fluorescence emission intensity, fluorescence intensity ratios of thermally coupled levels (H-2(11/2)/S-4(3/2)), and temperature sensitivity can be effectively controlled by changing the Ag concentration. When 0.15 mol% Ag is co-doped, the sensitivity of S-R in Ag@NaGdF4:Er3+ core-shell glass-ceramics reaches a maximum value. This work presents a new method to enhance emission intensity and optical thermometry ability of NaGdF4:Er3+ through constructing Ag@NaGdF4:Er3+ core-shell structure.