The structure and properties of the glass-ceramics were tested with X-ray diffraction testing instrument, correlative software, and other modern testing means. Then the effect of Al 2 O 3 content on internal stresses in CaO-Al 2 O 3 -SiO 2 glass-ceramics was studied deeply. In order to study the relationship of Al 2 O 3 to the residual stress of CaO-Al 2 O 3 -SiO 2 glass-ceramics, X-ray diffraction "sin 2 ψ" was used. The means utilized the x radial incidence produced from cathode radial tube, and took the space between crystals as measurement of strain. When the stresses produced, the space between crystals changed and the diffraction peak moved during Bragg diffraction. The magnitude of movement is related to the stresses. The experimental results show the residual stress is considerably high and Al 2 O 3 can influence the mechanical properties of this material hugely.