Abstract: The variation of fossil energy consumption, carbon dioxide and pollutant emissions are calculated after conventional fuel vehicles are replaced with electric vehicles based upon the full-cycle energy efficiency theory. The results show that the primary energy consumption, CO2, CO and HC emissions can be reduced with the substitution of electric vehicles for petrol vehicles, but NOx and SO2 emissions are increased. When diesel vehicles are replaced with electric ones, the emissions of pollutants except SO2 will be reduced, but the total emissions of CO2 and SO2 will be increased. Considering the proportion of coal-fired power generation to the total power generation in China, the target of energy saving and emission reduction cannot be thoroughly realized by the substitution of electric vehicles for oil-fired vehicles.