The aim of the present study is to find how the solvent polarity affects the liquefaction behavior of Chlorella pyrenoidosa and subsequently using the most suitable solvent identified to explore the solvent/biomass ratio, time, and temperature on the products yield and properties of the bio-oil. The products yield was significantly affected by the solvent type, and ethanol was proven to be the most suitable solvent to convert C. pyrenoidosa into bio-oil from the yield and economic points of view. Temperature is the most influential factor on the products yield and properties of the bio-oil. The HHVs of the bio-oils produced under different reaction conditions are within the range of 27.68-36.45 MJ/kg. The major compounds in bio-oil were esters, fatty acids, alkenes, aldehydes, and amides, and fatty acid ethyl esters were the largest portion. (C) 2013 Elsevier Ltd. All rights reserved.