Three constituents of loblolly pine (stem, residue, and bark) were independently pyrolyzed to produce light oil. The chemical structures of the light oils were analyzed using GC-MS, H-1 NMR, C-13 NMR, and HSQC-NMR. The experimental results indicate that levoglucosan observed in the light oil is the major product from cellulose pyrolysis. Furanic and phenolic monomers are derived from hemicellulose and lignin, respectively. The light oil hydrodeoxygenation reaction study was carried out using carbon-supported ruthenium as a catalyst. Light oils from all three constituents were independently upgraded under 8 MYa hydrogen gas at 300 degrees C for 2 h. After the upgrading process, the aromatic rings were hydrogenated and the oxygen-containing functional groups were extensively removed. According to H-1 NMR, the percentage of the CHnO peak area for stem, residue, and bark decreases by 90.03%, 77.84%, and 94.98%, respectively, compared to that for the pre-HDO light oil After upgrading, the carbon yields are 83.31% for the bark and approximately 100% for both the stem and the residue. The results indicate that ruthenium can hydrogenate carbonyl (C=O) bonds, furan ring, and aromatic ring as well as cleave the aliphatic C-O and C-C bonds by hydrogenolysis. However, it cannot cleave the ether and ester type bonds.