In this study, the conversion from Botryococcus braunii liquid to bio-jet fuel via a Ru/CeO₂ catalyst was conducted. At first, novel Ru/CeO₂ catalysts were prepared in order to increase the catalytic activity. “Ru/CeO₂-alcohol thermal” showed the highest activity: the squalane conversion exceeded 90%, an increase of about 22% in comparison with “Ru/CeO₂-impregnation”. When the B. braunii liquid was used as the raw material, no obvious catalytic activity was noticed. Therefore, the influence of impurities in the B. braunii liquid on the Ru/CeO₂ reaction were preliminarily analysed, confirming that the pigments (such as β-carotenoid) and the oxygen compounds (such as fatty acids) were the main factors influencing the Ru/CeO₂ reaction. Based on these results, the reaction process was optimized: prolonging the reaction time and pretreating the B. braunii liquid with H₂. Finally, the production of bio-jet fuel over Ru/CeO₂ was successfully achieved.