Chemical-looping gasification (CLG) of Chlorella vulgaris was carried out in a quartz tube reactor under different microwave pretreatment. The product fractional yields, conversion efficiency and analysis of performance parameters were analyzed in order to obtain the characterization and optimal conditions of microwave pretreatment for syngas production. The results indicate that microwave pretreatment is conducive to CLG reaction. Furthermore, the higher power or the longer time in the process of microwave pretreatment could not exhibit a better effect on CLG. In addition, 750 W and 60 s is the optimal microwave pretreatment power and time respectively to obtain a great reducibility of oxygen carrier, high conversion efficiency, high products yield and good LHV. The H-2 yield, LHV, gasification efficiency and gas yield increased obviously from 18.12%, 12.14 MJ/Nm(3), 59.76% and 1.04 Nm(3)/kg of untreated Chlorella vulgaris to 24.55%, 13.13 MJ/Nm(3), 72.16% and 1.16 Nm(3)/kg of the optimal microwave pretreatment condition,respectively. (C) 2017 Elsevier Ltd. All rights reserved.