The high dense amorphous Si-B-C-N bulk ceramic was fabricated at 1000~1600℃ under a pressure of 5 Gpa for 30 min where the mechanically alloyed amorphous SiBCN powder was used as raw material.The crystallization and microstructure evolution behaviors of the prepared ceramics were carefully investigated by XRD,TEM and HRTEM.Results show that,at or below 1100℃,the ceramic lies in an amorphous state.