The invention provides a tapered sleeve and a manufacturing method thereof. The tapered sleeve is a silicon nitride ceramic sleeve, and a casting part is also arranged on the outer wall of the tapered sleeve. The manufacturing method comprises the following steps: step one, drying a silicon nitride ceramic sample in a vacuum drying oven for 48 to 96 hours, wherein the drying temperature is 35 to 70 DEG C; step two, sintering the dried silicon nitride ceramic sample in an atmosphere pressure sintering furnace under nitrogen protection, wherein the sintering temperature is 1720 to 1800 DEG C, and a heating rate is 0.5 to 2 DEG C/min; keeping warm after a temperature in the atmosphere pressure sintering furnace reaches the sintering temperature, wherein the sintering time is 1 to 2 hours. Since the tapered sleeve provided by the invention is manufactured by adopting high heat-resisting and wear-resisting silicon nitride ceramics, the tapered sleeve has good wear resistance and good heat conductivity; meanwhile, the heat dissipation speed is fast, and a wear rate of the tapered sleeve is reduced, so that the service life of the tapered sleeve is prolonged.