The invention relates to a 
system for reducing emission of oxynitride of 
combustion equipment. The 
system comprises the 
combustion equipment with a burner and a 
flue. A gas flow adjusting valve is installed on a pipeline connecting the burner with a gas source. The 
flue is internally provided with a sensor used for detecting the concentration of gas components. An air inlet of the burner is connected with an air outlet of an air mixer in series. The air mixer is provided with two air inlets, one of the air inlets is connected with a 
combustion-supporting air pipeline with an 
air volume adjusting valve, the other air inlet is connected with a 
smoke gas returning pipeline with a 
smoke gas returning flow adjusting valve, the other end of the 
smoke gas returning pipeline is connected with the position, between the combustion equipment and the sensor, of the 
flue, and an 
air blower, the 
air volume adjusting valve, the smoke gas returning flow adjusting valve and the gas flow adjusting valve are controlled by a low-
nitrate controller. The invention further relates to a method for reducing emission of the oxynitride of the combustion equipment. The problem that combustion is not stable in the operation process of an existing smoke gas outer circulation 
system is solved.