Abstract: Catalytic hydroprocessing of the bio-oil obtained through fast pyrolysis of Chlorella was carried out in a bench-scale continuous-flow fixed-bed reactor equipped with a Ni-Co-Pd/γ-Al₂O₃ catalyst. The effects of the hydrogenation temperature and the H/oil molar ratio on the moisture content, calorific value, viscosity and cetane number of the refined bio-oils were investigated at the pressure of 2×10⁶ Pa, It was shown that the yield of the refined oil reached 86.1%, and the calorific value and cetane number were increased by 17.94% and 71.2% respectively, while the viscosity was decreased by 66.32% at the temperature of 300 ℃, the pressure of 2×10⁶ Pa and the H/oil mol ratio of 120. The elemental analysis and GC-MS analysis results of the bio-oil before and after hydrogenation show that the H/C mol ratio was increased from 1.55 to 1.97, while the oxygen, nitrogen and sulfur contents were significantly decreased. The deoxidation degree reached 80.46%. The amounts of organic acids, esters, ketones and aldehyde in the refined oils were obviously decreased, while those of alcohols and alkanes were markedly increased.