Abstract: Impact Pathway Analysis and Life Cycle Analysis approaches were applied to establish an accounting framework of externalities of the nuclear power chain and coal power chain.Comparative assessment of the external costs of environmental impacts from nuclear power and coal power was carried out.The results are:air pollutant emissions from the coal power chain leads directly to environmental effects of acid rain,dust deposition and global warming.Obvious impacts of air pollutant emissions from the coal power chain on human health,crops and forests,materials and cleanliness can be observed,while no perceivable impacts have been found from the nuclear power chain.The SO₂,NO_x,PM and CO₂ emission factors from the coal power chain are two orders of magnitude higher than those from the nuclear power chain;the radiation impact of the coal power chain is 40 times higher than that of the nuclear power chain;and,the total external cost of the coal power chain is 115 times higher than that of the nuclear power chain.According to the comparison results: ①nuclear power is clean and more environmentally-friendly than coal power; ②coal-based energy structure is one main reason for environmental problems in China; ③environmental values are not reflected reasonably in the present energy pricing mechanism.The way to achieve sustainable energy development could be via saving energy and enhancing energy utilization efficiency,optimizing energy structure,developing clean energy technologies,and internalizing the externalities by improving the energy pricing mechanism.