Abstract: In recent years,the installed capacity of wind power generation and solar power generation is growing rapidly.In order to improve the absorption capacity of new energy,the flexible operation of coal-fired units is the general trend.At present,large-capacity power station boilers are generally equipped with direct-blowing pulverizing system,and the large deviation of pulverized coal and air distribution in the outlet air pipe of coal mill is a common problem.With the development of flexible operation of the unit,large deviation of pulverized coal and air distribution directly limits the flexible operation of the unit.In this paper,the reasons for the large deviation of pulverized coal and air distribution of the coal mill outlet parallel primary air duct were analyzed from the point of view of the pulverizing system equipment.Various problems in the boiler operation process caused by the large deviation of pulverized coal and air distribution,such as flame deflection,coking,high temperature corrosion,high NO_x emission,high fly ash fuel and low boiler efficiency,were described.The problem is especially serious in the process of unit flexibility transformation.During low-load operation,the deviation of pulverized coal and air distribution will increase ignition distance of the boiler,resulting in unstable combustion and even extinguishing the fire. Uneven heat load in the furnace will aggravate the deviation of the steam in the boiler,worsen heat transfer,and overheat the heating surface,which will directly affect the operation safety of the unit.In order to improve the deviation of pulverized coal and air distribution.the performance advantages and disadvantages of pulverized coal distributors were analyzed,and the application and effect of pulverized coal distributor in power station boiler in recent years were introduced.Therefore,with the development of flexible operation,it is necessary to reform the pulverizing system of flexible operation units,install the matching coal powder distributor,improve the pulverized coal and air distribution characteristics,and improve the operation stability and safety of units.