Electric shared micromobility has been popularized and developed worldwide in recent years. However, its environmental impact remains unclear. Based on user travel behavior and actual operational data, a life cycle assessment (LCA) study quantitatively estimates the environmental impacts of China's free-floating e-bike sharing (FFEBS) promotion, including human health, ecosystems, and resources. The results show that the low utilization makes FFEBS not an environmentally friendly mode of transportation. Taking into account the travel mode shift towards FFEBS, under the current operating efficiency of FFEBS, the substitution rate of car travel needs to reach about 40% to obtain environmental benefits. However, FFEBS can barely obtain environmental benefits on fine particulate matter formation, Human toxicity, Ozone formation, Freshwater and Marine eutrophication, Terrestrial acidification, and Terrestrial ecotoxicity, which is largely attributed to the negative effects of batteries and electronic components and the required rebalancing and recharging activities. As utilization continues to increase, it is estimated that each kilometer of FFEBS trips could reduce the impact of fossil resource scarcity and global warming by up to about 11.87 g oil eq and 32.06 g CO2-eq, respectively. This empirical study can not only help authorities, operators and the public better understand the environmental impact of FFEBS, but also provide a valuable reference for formulating effective measures to improve the sustainability of the FFEBS and urban transportation systems.