Abstract: Based on the qualitative analysis of light oil from biomass alcoholysis, the thermogravimetry simulation and real distillation processes were performed to study the feasibility of separation of valuable chemicals from light oil. The results showed that the distillation processes could be divided into four stages: a) room temperature-141 ℃; b)141-207 ℃; c) 207-280 ℃ and d) 280-400 ℃. Near 70% fraction was distilled before 207℃. It was found that condensation reaction took place even at the first stage under the temperature of 141 ℃, which resulted in the formation of water. During this stage, 1-octanol could be entrained with the water in distillation process. At the second stage of temperature between 141-207 ℃, an azeotropic system was formed by 1-octanol, formic-acid-octyl-ester, acetic-acid-octyl-ester, and minor hexanoic-acid-4-octyl-ester as well as octyl-ether. Finally, the FTIR analysis on the distillation residue showed that aldol condensation and dehydration reaction took place during the distillation processes, which resulted in the formation of aromatic compounds and ethers.