Abstract: Hexadecyl ether of arabinogalactan (HEAG) was synthesized by Williamson reaction, using chlorohexadecane and arabinogalactan (AG) extracted from Larix gmeini Rupr. wood as reagents, dimethylsulfoxide as solvent, and sodium hydroxide as catalyst. The influences of time, temperature and the ratio of chlorohexadecane to AG were discussed. The results obtained showed that average substitution degree of HEAG was 0.212 mmol/g and the yield was 65.56%, under the conditions of reaction time 30 min, temperature 25℃, and reagent ratio 0.3:1(mL:g). Determinations of surface tension and lipophilicity indicated that the lipophilicity of HEAG was better than that of AG, with an increase of solubility at 30.66% and 21.95% in hexane and petroleum ether respectively, while a decrease of 60.90% and 44.24% in chloroform and water respectively. The solubility of HEAG is 6.70 grams in 100 g water.