Abstract: Grignard reagent benzylmagnesium chloride was synthesized using a sonochemistry method. The effects of solvent types, temperature, raw material mol ratio, magnesite powder states and stir situation on the yield of products under fixed ultrasonic power and frequency was studied. Based on the studies the orthogonal experiment was carried out to optimize the factors. Gas chromatogram was performed to analyze the products qualitatively and quantitatively, showing the optimum conditions: fresh magnesium powder and benzyl chloride as raw material, solvent being THF, ether or solution of THF and ether, water bath temperature 20℃ and unstirred, and the yield 81%.