Using corn stover as a raw material to produce fuel ethanol has good application prospects. The processes of ethanol synthesis from corn stover using direct and indirect thermochemical conversion methods have been developed. After the system boundaries were determined, a life cycle assessment was conducted to evaluate whether the two processes would be environmentally friendly. It was found that the energy efficiency of direct ethanol synthesis process (direct case) was lower (0.38) than that found for the indirect process (indirect case), which was 0.41. The same tendency was found with the alcohol yield. The alcohol yields in the direct case and indirect case were 23 and 30 wt %, respectively Then, the environmental impacts including global warming potential and acid potential of the two processes were compared and discussed. Finally, the distribution of the environmental impact values for the two ethanol synthesis processes was presented. With regard to the environmental impact, the indirect case was superior to the direct case, showing good promise in future applications.