The invention provides a supercritical technology-ultrasonic wave-based method for separating and refining beta-methylnaphthalene. The method comprises the following steps of: treating a methylnaphthalene fraction firstly by using an
aqueous solution of
ammonium bisulfate, adding
ethanolamine, conducting even mixing by using a pre-mixer, transferring the mixture to a supercritical reactor, raisingthe temperature to 180 DEG C at a rate of 20-25 DEG C / min, performing cool stirring by introducing
condensed water, then decreasing the temperature to 166-168 DEG C at a rate of 5-10 DEG C / min, performing a constant temperature reaction for 1-6 h, stopping heating, and performing separation and collection on gas-liquid products to obtain a
nitrogen-removed methylnaphthalene composition; preheating the composition to 65-75 DEG C, adding an
acetic anhydride catalyst and
hydrogen peroxide slowly and dropwise, performing high-speed stirring for 60-90 min under the action of ultrasonic
waves at 70-80 DEG C, performing extraction and rectification to obtain a
sulfur-removed methylnaphthalene composition, adding
ethylene glycol into the
sulfur-removed methylnaphthalene combination, heating the mixture to 190-195 DEG C under the action of ultrasonic
waves, collecting gas, condensing the collected gas to obtain a high-purity alpha+
beta methylnaphthalene composition, then placing the high-purity alpha+
beta methylnaphthalene composition in a freezing
microtome, performing freezing crystallizing at -25-(-15) DEG C, performing separation, and performing redissolving to prepare the beta-methylnaphthalene at 36-38 DEG C.