High h-BN ceramics were prepared by an oscillatory pressure sintering technique (OPS), and the effect of oscillatory pressure on the sintering densification and grain growth of h-BN ceramics was investigated. Boron nitride ceramics were also prepared by a hot pressing sintering process (HP). The density, microstructure, fracture reliability, degree of grain orientation, mechanical and thermal properties of boron nitride ceramics at different sintering processes were analyzed. The results show that the fracture surface of OPS specimens is denser, and the grain orientation becomes clear, compared with those of HP specimens. A high proportion of parallel-arranged BN grains can effectively improve the densification of BN ceramics. The maximum hardness, fracture toughness and flexural strength of OPS specimens are 0.31GPa, 1.09MPa?m1/2 and 74.4MPa, respectively, which are greatly improved, compared with HP specimens at the same sintering parameters. According to the data of grain orientation determined by X-ray diffraction patterns, the application of oscillatory pressure obviously promotes the densification and sintering of boron nitride ceramics, thus improving the fracture reliability and thermal conductivity.