Abstract: A series of experiments of microalgae pyrolysis using microwave were carried out. The influences of different additives such as activated carbon, H₃PO₄, NaOH, MgCl₂, MgO on microalgae pyrolysis were examined. The weight loss during pyrolysis of microalgae with different microwave powers (200, 600, and 900 W) were studied. The result shows that there are four stages in microalgae pyrolysis: dehydration, drying, rapid pyrolysis and slow pyrolysis. All the additives improve the yield of solid product significantly, but reduce the gaseous yield; and have no remarkable influence on the liquid yield. However, H₃PO₄ and MgCl₂ raise the liquid yield, NaOH is opposite. The corresponding activation energy of microalgae rapid pyrolysis was obtained by Flynn-Wall-Ozawa method (FWO), and the value generally increases with the deepening of the reaction.