Abstract: Machinable ceramics h-BN/Al/SiC with high hardness were produced by pre-sintered in plasma activated sintering system(PAS) and then heat treated in a vacuum furnace.Firstly,the ceramic composites of h-BN/Al/SiC were pre-sintered in PAS system.For the high heating rate of PAS,during the pre-sintered process,h-BN/Al/SiC composite was in high density;after subsequent heat treatment,the hardness was improved.X-ray diffraction(XRD),the different phase of h-BN/Al/SiC composite between pre-sintered and subsequent heat treatment were discussed.The effect of the Al content on the composites,density,hardness,toughness had been investigated.The results showed that after PAS pre-sintered,the SiC composite had higher density with Al content increased;After subsequent heat treatment in the vacuum furnace with higher temperature,the hardness and toughness of the SiC machinable ceramics can be improved much more for the new ceramics phases were formed.