In this study, hydrothermal liquefaction (HTL) experiments of Nannochloropsis and Spirulina were carried out at different temperatures (220-300 degrees C) to explore the effects of temperature on bio-crude yield and properties. The optimal temperature for bio-crude yield was around 260-280 degrees C. Transfers of element and chemical compounds in bio-crude were discussed in detail to deduce the reaction mechanism. The hydrogen and carbon recoveries were consistent with the results of bio-crude yields at every temperature point. The relative percentage of fatty acid in bio-crude decreased and the amine and amide increased for both microalgae with temperature rising. The N-heterocyclic compounds in bio-crude increased with temperature rising for Nannochloropsis, while decreased when temperature increased from 220 degrees C to 280 degrees C for Spirulina. Bio-crude gained at higher temperature or from microalgae with high protein content may contain high heteroatom compounds. (C) 2015 Elsevier Ltd. All rights reserved.