This paper describes catalytic consequence of hydrothermal liquefaction (HTL) of Dunaliella tertiolecta (D. tertiolecta) over carbon nanotubes (CNTs) supported metals catalysts to produce bio-oil. When Co/CNTs is used as catalysts, the conversion and bio-oil yield increase to 95.78 and 40.25 wt.%, respectively. Chemical analysis results showed that the introduction of catalyst significantly affected the chemical composition of bio-oil with a higher percentage of hydrocarbons and a lower content of fatty acid. The introduction of metal into CNTs had no change in the basic CNT skeleton and the loaded metal nanopartides encapsulated within the CNT enhances the disorder and defects in CNTs. Based on our results and the literature, the plausible general reaction and catalytic HTL pathways of D. tertiolecta are proposed. (C) 2016 Elsevier Ltd. All rights reserved.