The life cycle assessment of a fast pyrolysis scenario for bio-oil production was conducted to evaluate whether the process would be environmentally friendly. The net energy value (NEV), energy consumption, global warming potential (GWP), acidification potential (AP) and some other environmental impact values in the life- cycle stage of biomass fast pyrolysis system were discussed. The net energy value was 0.68 MJ/MJ, and global warming potential was 0.0565 CO_2-Equiv.kg/MJ. The normalization and weighting results of these environmental impact values were analyzed to investigate the impact distribution of in the different stages of life cycle of biomass fast pyrolysis. The results show that the biomass fast pyrolysis technology is environmentally friendly and hopefully, and can make positive contribution to climate change and environmental pollution problems.