Abstract: Based on emission factors and historical energy consumption statistics,NO_x emission inventory in Liaoning Province from 1980 to 2003 was studied.Temporal variations were described and contributions from different sources(fuels,sectors) were estimated.The results showed that total amount of NO_x emission increased by an annual growth rate of 4.30%,despite fluctuations in some years.In 2003,NO_x emission amount was 108×10~4 t.The increase of NO_x emission basically coincides with the increase of energy consumption.Contribution from coal consumption was the dominant source of NO_x emission,which accounted for 65% of the whole amounts,and the highest emission was in 2003,reaching 10.17×10~4 t.About 90% NO_x was generated from energy transformation,industry and transportation sectors,and 28.10%～40.85% of the total amount was generated from power industry,which will continue to be the dominant source of NO_x emission in Liaoning Province in the future.The contribution from transportation sectors increased year by year and the trend was more evident after the year 2000.