B4C composite ceramic with different amount of CaB6 was prepared by hot pressing under1900 1C, 30 Mpa ,1h. The results showed that the density of B4C composite ceramic rose with the increase of CaB6 amount ; hardness rose in value with an increasing of CaB6 up to15wt% and decreased at higher amount .In addition, corrosion behavior of B4C composite ceramic in simulated seawater was studied. The maximum quality change rate and maximum corrosion current density in the simulated seawater were1.31×10-2 mg×cm-2 × d-1 and 1.058×10-5 A/cm2, Respectively , which showed B4C composite ceramic had excellent corrosion resistance in marine environment.