Abstract: The article mainly studies emission characteristics of combustion pollutant after mixing petroleum coke in coal-pulverized boiler.The mixture particle size influences its combustion properties,and thus indirectly effects NO_x and SO₂ emission.The SO₂ concentration of flue gas becomes higher and higher with increasing excess air coefficient,and when the excess air coefficient is between 1.3 and 1.4,the concentration of NO_x in flue gas reaches the highest.The combustion adjustment results in power plant are in agreement with experimental results in the laboratory.In order to decide appropriate particle size and mixing ratio in practical production in coal-fired power plant,we should consider comprehensively how the particle size,ratio and content (N and S) of mixture influence combustion properties and emission of NO_x and SO₂.