β-alkoxynaphthalenel was prepared from β-naphthol and H(CH₂)_n Br under nitrogen in the supersonic waves. Sodium methoxyide and methanol was solvent.The yield was 94%. The reaction conditions: molar ratio of β-naphthol/H(CH₂)_n Br was 1,condensation of sodium methoxide was 2.0 mol/L,supersonic ratio was 33±2kHz,reaction time was 5h.