Bio-oil, with high oxygen-containing character, which was prepared from flash pyrolysis of rice stalk powders, was upgraded by the method of catalytic esterification with methanol. The esterified oil was distilled stepwise from 60 °C to 105 °C, and the fractions were analyzed with Fourier transform infrared spectroscopy (FTIR) and gas chromatography/mass spectroscopy (GC/MS) for the distribution of species. It was found that 58% of the components were detected in the fraction of 60 °C-80 °C, with 1,1-dimethoxypropan-2-one was the most abundant species. The residue, in which the boiling point of species were higher than 105 °C were resolved in acetone, and also analyzed with GC/MS. The results showed that phenols are the most abundant species, and following the ketones and hydrocarbons.