Abstract：Microalgae biodiesel is a complex industrial energy production method that is influenced by many factors including the complex composition. The energy consumption and generation ability and the amount of greenhouse gas emissions (net carbon emissions) are important criteria for assessing the system sustainability. A life cycle analysis of the energy and carbon balance of microalgae biodiesel were used to calculated the net energy surplus and net carbon emissions of biodiesel biofuel and the key factors influencing the energy production and carbon emissions. The results show that the energy output of the whole system is larger than the energy consumption during the production and processing of the microalgae biodiesel and that more CO2 is fixed than released over the life time. Thus, microalgae biodiesel is a new fuel that is sustainable and environmentally friendly.