Abstract: 1-Methyl-3-benzylimidazliu chloride ionic liquid (BzmimCl) was synthesized by ultrasonic assistance, and its structure was characterized by UV and FT-IR spectra. The influences of the reaction conditions on the yield of BzmimCl were investigated, and the experimental results showed that the application of ultrasonic wave intensified the synthesis process of ionic liquids and reduced the synthesis time. The optimum synthesis condition was obtained as follows: power of ultrasonic wave 100 W, reaction temperature 80℃, reaction time 1 h and the molar ratio value of benzyl chloride to 1-methylimidazole were 1.1. The yield and purity of the ionic liquid under the optimum condition were 99.8% and 98 %, respectively. The dissolution of the Chinese fir sawdust activated in the ionic liquid was discussed under different temperature, and the solubility of the sawdust is 5.4 at 120℃.