Abstract: Nannochloropsis sp. was pyrolyzed directly or with H-ZSM-5 as catalyst under nitrogen atmosphere to produce bio-oil. The influence of pyrolysis temperature on the product distribution in the pyrolytic oil was investigated within the range of 573K～773K. Compared with the pyrolysis of lignocellulosic biomass, the pyrolysis of Nannochloropsis sp. can be performed at relatively lower temperature and with higher oil yield. H-ZSM-5 is effective for the removal of various polar functional groups as well as for the aromatization; and the bio-oil obtained with H-ZSM-5 catalyst contains more aromatic compounds and fewer polar species than that from direct pyrolysis. The heating values of the bio-oil from Nannochloropsis sp. is higher than that from lignocellulosic biomass, and thus the former is more suitable to be upgraded to practical fuel.