Aluminosilicate oxynitride and cubic boron nitride (cBN) composites having excellent mechanical properties andchemical stability in room temperature to high temperature applications. In the present study, cubic boron nitride (cBN)reinforcedalpha-Sialonnano-composites were preparedusing spark plasma sintering (SPS) technique. The starting powdersincluding Sialon precursors and various particles size of cBN (10, 20 and 30 wt.%) were homogeneously mixed by probesonication before sintering. The effect of SPS processing parameters on the densification and mechanical behavior of thesenano-composites were investigated. These cBN enabled in the densificationsialon composite samples were analyzed for phaseidentification by X-ray diffraction. As well as, composite samples were evaluated to find cBN to hBN transformation in theSialon matrix sintered at 1500°C. Field emission scanning electron microscopy(FESEM) used for morphology and hardnessand fracture toughnesswere measured.