Gas pressure sintering law. Because silicon nitride is sintered at 1~ 10MPa and around 2000℃, high nitrogen pressure inhibits the high-temperature decomposition of silicon nitride, and can also promote the growth of Si3N4 grains with less sintering AIDS. Finally, the prepared samples are long columnar grain ceramics with high density and high strength. The method has high density, high strength and good wear resistance, and can be manufactured. Silicon nitride ceramic is an inorganic material ceramic that does not shrink when sintered.