Wind power is widely regarded as a clean, low-carbon, and alternative energy source for coal-fired power. However, quantitative studies of wind power are limited in indicating the differences in environmental impacts as compared with coal-fired power. Therefore, a life cycle assessment (LCA) is utilized to compare the environmental emissions from wind and coal power. Based on LCA results, material and energy flow of wind power are depicted, and its substitution effects are estimated. For 1 kilowatt-hour (kWh), wind power only consumes 4% of the total amount of carbon dioxide (CO2) emissions and environmental costs related to coal power. Furthermore, energy and emissions intensities of wind power are concentrated in the manufacturing stage, while those of coal power focus on the operation and maintenance stage. In addition, the environmental costs of the construction stage of wind power are slightly higher than that of the production and manufacturing stage due to the using of purchased electricity, accounting for 47% of the total environmental costs. Based on a consequential LCA, the mitigation potential of CO2 emissions of wind power is estimated to be less than 500 million tons during the period of China’s 12th Five-Year Plan (5 years). More than 300 million tons reduction is expected to be realized in 2020. Finally, some policy implications for Chinese policymakers are proposed to promote the development of the wind power industry.