The fast pyrolysis of microalgae (MA) over oil shale (OS) were carried out in an analytical Py-GC/MS. The effects of pyrolysis temperature and OS percentage on products distribution and selectivities of aromatics were investigated. 600 degrees C was the optimum temperature, given the total peak area of volatile matters and the yields of aromatics, alcohols and phenols. OS significantly increased the yields of hydrocarbons, phenols and ketones, while decreased the yields of acids and alcohols. The maximum yields of aromatics (35.01%) and the minimum yields of acids (42.72%) were obtained at a OS content of 3%. During the co-pyrolysis process, the high FIX ratio of OS accelerated the production of hydrocarbons by catalytic cracking and reforming, and the oxygenates content decreased by 24.4% due to the ketonization and aldol condensation. The formation of polycyclic aromatic hydrocarbons was inhibitted, which was beneficial to improve the anti-coke ability of catalyst and the quality of pyrolytic oil. A significant synergistic effect between MA and OS was achieved at the OS percentage of 3% by the comparison of experimental results and calculated values of aromatics. (C) 2018 Elsevier Ltd. All rights reserved.