Fig. 3 was the density curve of B4C composite ceramic with different amount of CaB6. It can be seen that the relative density of B4C composite ceramic rose with the increase of CaB6 amount. Fig. 5a to Fig. 5e were the fracture surface SEM of B4C composite ceramic. The black part and white part in the picture of Fig. 5 were B4C phase and CaB6 phase confirmed by EDS,respectively. It was obvious that with the CaB6 amount increased, the volume of CaB6 in the B4C composite ceramic largened, which would form more grain boundaries that can promote the sinter ability of ceramic.