The expanding population and the transformation of consumption structure are the key factors that affect the sustainable development of national economy and the sustainable use of re- sources in an all-round way．This paper measures the environmental efficiency by super-efficiency DEA method，and studies the impact of population size and consumption structure on environmental efficiency based on the STIRPAT model．The results show that from 2000 to 2013，the environmental efficiency of China's provinces demonstrated a declining trend of volatility with large regional differences．At this stage，the expansion of the population size has a negative impact on the environmental efficiency in China．Meanwhile，consumption structure，as an important intermediate variable linking population and environment，shows different relationship patterns with environmental efficiency according to different types of consumption structure．Specifically，the relationship between subsistence and enjoyment consumption with the environmental efficiency has a u-shape，the inflection points of which are 60． 18% and 29. 20% ， while the relationship between development consumption and the environmental efficiency shows a line- ar positive correlation．With the upgrade of consumption structure，the negative impact of population size on environmental efficiency will be altered．