The pyrolysis of Chlorella vulgaris was carried out in a quartz tube reactor with different catalysts and contents of activated carbon. The solid residue yield, gaseous products and the evaluation method based on higher heating value and energy consumption were analyzed in order to obtain the optimal condition to produce syngas. The results indicated that catalysts obviously affected the pyrolysis products. Activated carbon was a good choice of catalyst to obtain the minimum solid residue yield (10.79 wt.%), and mixing with a higher content of activated carbon could produce a lower solid residue yield; meanwhile, the effect of each 1% activated carbon will be worse. According to the evaluation methods, there was a certain impact on the syngas production under different catalysts and contents of activated carbon. Furthermore, the HVe,s indicated that activated carbon was the optimal catalyst and 3% is the optimal content of activated carbon to produce syngas. (C) 2014 Elsevier Ltd. All rights reserved.