There have been severe haze and smog descending over northern China since 2012 and posed a great deal of health, environmental and society problems. Beijing, Tianjin and Hebei are the most heavily polluted region in North China. In order to identify which energy sector play most significant role in haze and smog pollution in Beijing, Tianjin and Hebei, this paper has characterized emission inventories of nitrogen oxides (abbr. NOx) and total suspending particulate matters (abbr. TSP) of 9 energy sectors (power, heating, industry, construction, transportation, urban domestic, rural domestic, commercial buildings and others) in 2012. It is found that during winter time, when severe smog and haze pollution tend to occur, heating and industry sectors were the major causes for smog and haze pollution, corresponding average proportions of NOx and TSP emissions were 32% and 38%, respectively. Contributions of other important sectors to smog days in winter were: power (15%), domestic (9%) and traffic (7%). This implies that government should start with controlling heating emissions, especially in Beijing, and effective NOx and dust removers should be applied to industries to reduce NOx and TSP emissions and thereby mitigating the haze and smog pollution effects.