MgO-Al2O3-SiO2 glass-ceramics containing 4.0w% alkali oxides were prepared by conven- tional melt quenching technique. The effects of heat treatment conditions on crystal types, microstructure and break strength of the glass-ceramics were studied by DSC, XRD, SEM and break strength tests. The main crystallization phases of this glass system are β-quartz (Li2-2xMgxAl2Si3O10) and β-Spodumene, no cordierite phase found. The glass-ceramics possessed a regular network-shaped microstructure feature formed by pyroxene crystals. With the increase of temperature, the β-Quartz around pyroxene crystals converted into β-spodumene and the regular network-shaped microstructure feature getting weaker and disappeared. The average break strength of the glass-ceramics containing no cordierite crystals based on MgO2-Al2O3-SiO2 system is about 150MPa, which is much high than the base glass.