Biomass conversion via pyrolysis has been regarded as a promising solution for bio-oil production. Compared to fossil fuels, however, the pyrolysis bio-oils from biomass are corrosive and unstable due to relatively high oxygen content. Thus, an upgrading of bio-oil is required to reduce O component while improving stability in order to use it directly as fuel sources or in industrial processes for synthesizing chemicals. The catalytic hydrodeoxygenation (HDO) is considered as one of the promising methods for upgrading pyrolysis bio-oil. In this research, the HDO was studied for various catalysts (HZSM-5, metal, and metal-phosphide catalysts) to improve the quality of bio-oil produced by fast pyrolysis of Saccharina japonica (SJ) in a fluidized-bed reactor. The HDO processing was carried out in an autoclave at 350 °C and different initial pressures (3, 6, and 15 bar). During HDO, the oxygen species in the bio-oil was removed primarily via formation of CO₂ and H₂O. Among the gases produced through HDO, CO₂ was observed to be most abundant. The C/O ratio of produced bio-oil increased when CoMoP/γ-Al₂O_3, Co/γ-Al₂O₃, Fe/γ-Al₂O₃, or HZSM-5 was used. The Co/γ-Al₂O₃ resulted in higher HDO performance than other catalysts. The bio-oil upgraded with Co/γ-Al₂O₃ showed high HHV (34.41 MJ/kg). With the use of catalysts, the kerosene-diesel fraction (carbon number C₁₂–C₁₄) was increased from 36.17 to 38.62–48.92 wt.%.