Coal-to-olefin (CTO) projects, an energy strategy, are increasing in number in China but suffer from high consumption and pollution. In this study, a life cycle assessment is studied to determine whether oil field gas-assisted CTO systems have the potential to solve these problems. Oil-to-olefin is presented for comparison. Results showed that the current CTO scenario generally exerts a higher environmental impact than oil-to-olefin. The effects on carcinogens, climate change, and fossil depletion, which were provided mainly by chromium to water, carbon dioxide to air, and hard coal consumption, respectively, are the main contributors to the environmental burden. Oil field gas-assisted coal-to-methanol production decreases the potential impact on climate change, carcinogens, and fossil depletion by 40%, 9%, and 50%, respectively, because it consumes less coal (>73%) than conventional coal-to-methanol production. Oil field gas-assisted CTO is an attainable and effective means of carbon reduction in the CTO industry in China. It is highly recommended for further improving the environmental performance of the CTO industry. (C) 2018 Elsevier Ltd. All rights reserved.