Energy release rate and fracture toughness of amorphous aluminum nanoparticles reinforced soda-lime silica glass (SLSG) were measured by performing fracture simulations of a single-notched specimen via molecular dynamics simulations. The simulation procedure was first applied to conventional oxide glasses and the accuracy was verified with comparing to experimental data. According to the fracture simulations on three models of SLSG/-Al2O3 composite, it was found that the crack propagation in the composites is prevented through following remarkable phenomena; one is that a-Al2O3 nanoparticles increase fracture surface area by disturbing crack propagation. The other is that the deformation of a-Al2O3 nanoparticle dissipates energy through cracking. Moreover, one of the models shows us that the crack cannot propagate if the initial notch is generated inside a-Al2O3 nanoparticle. Such strengthening is partly due to the fact that the strength of the interface between nanoparticle and SLSG matrix is comparable to that of SLSG matrix, implying that their interface does not reduce crack resistance of the oxide glass.