β-naphthyl methyl ether was synthesized in the presence of a new kind of cheap and effective environmental friendly solid catalyst H2SO4/Carbon under ultrasonic irradiation. The influences of catalyst’s dosage, methanol consumption , the reaction time，ultrasonic power on the yield of product have been investigated. Get the optimal reaction conditions as follow: the mole ratio of β-naphthol and methanol is 1:6, amount of catalyst is 7mol%，ultrasonic power is 200W，reaction time is 15min and temperature is 80℃. Under the optimal reaction condition, the yield of β-naphthyl methyl ether is 98.3%. The reaction condition is mild, the method is simple and efficient.