Crystallization sequence of MgO-Al2O3-SiO2-TiO2 system glass was investigated by means of DTA, XRD, SEM and EDS. The relationship between crystalline phases, heat treatment methods and thermal expansion coefficient (α) were well discussed. The results have shown that: The glass first underwent extensive phase separation into titanium-rich droplets in a silica-rich matrix, then magnesium aluminotitanate (MAT) initially precipitated in the droplet phases. With the crystallization temperature increased, β-quartzss, sapphirine, α-quartzss and α-cordierite made their appearance successively. The thermal expansion coefficient as a function of the heat treatment condition was studied.