Onshore and offshore wind turbines may have different environmental sustainability due to their owncharacteristics, and this information is important for future growth of wind power. The paper uses lifecycle assessment (LCA) to estimate the life-cycle greenhouse gas (GHG) emissions of onshore andoffshore wind turbines with the nominal capacity of 2 MW, to advance our understanding of onshore andoffshore wind energy and to inform policy, planning, and investment decisions for future growth of windpower. Results show that the life-cycle GHG emission intensity is 0.082 kg CO2-equivalent (eq)/Mega-joule (MJ) for onshore wind turbine and is 0.130 kg CO2-eq/MJ for offshore wind turbine, respectively.Offshore wind turbine has larger life-cycle GHG emissions than onshore wind turbine, owing to thefloating platformfixed in sea. Onshore and offshore wind turbines have much smaller life-cycle GHGemission intensity than coal power plants. If the installed wind turbines in 2014 displace coal, the savedGHG emissions can roughly reach 5.08x107tCO2-eq, accounting for 0.09% of global GHG emissions in2012. The sensitive analysis shows that the lifetime and energy production of wind turbine have largeinfluences on the GHG emission intensity of both onshore and offshore wind turbines, implying that it isan effective way to prolong the lifetime of wind turbine and increase the energy production of windturbine to reduce the GHG emission intensity of wind turbine. The sensitivity analysis further shows thatthe distance from wind turbine factory to wind farm site has more significant influence on the life-cycle GHG emission intensities of both onshore and offshore wind turbines than that from wind farm site tothe recycling and landfill locations, suggesting that the wind farm site and the wind turbine factoryshould be as close as possible.