Abstract: The bio-oils from ordinary condensation and from fractional condensation were analyzed by GC-MS. Comparing the relative peak areas of these, the result shows that the fractional condensation has an obvious effect on component enrichment. The acetic acid in the 4th step condensation increases from 5.38% to 9.44%, the guaiacol in the 2nd step condensation increases from 3.46% to 6.23%, and the sringol and isoeugenol in the 1st step condensation increase from 1.48% to 4.44% and from 5.52% to 17.84%, respectively. After 75 days' storage stability experiment on the physicochemical properties of multi-fraction bio-oils obtained from fractional condensation in a 15℃ constant temperature and humidity box, the water content of the fractional bio-oils increases by 1.58%, 1.88%, 1.80% and 2.43%, respectively. Besides, the acids, aldehydes, ketones and alcohols decrease after storage because light components are consumed by chemical reaction. The relative peak areas of phenols increases slightly. It suggests that the chemical reactions in the bio-oil from 1st and 2nd step condensations can be negligible, while the chemical reactions in the bio-oil from 3rd and 4th step condensations are active. Organics in bio-oils can be classified by the analysis of GC-MS both before and after storage for analyzing the kinds and intensities of the chemical reactions in bio-oils.