Abstract: The A coal mill of a certain unit has repeatedly experienced unexpected inlet air volume jump faults about 20 minutes after startup. This fault causes a large amount of pulverized coal to rush into the furnace instantly, leading to a rapid rise in superheat degree. Consequently, all levels of desuperheating water valves are forced to open fully, which seriously affects unit thermal efficiency and the safety of boiler heating surfaces. By tracing the fault process and analyzing causes with historical operation data, this paper identifies the root cause as abnormal locking logic of air volume calculation triggered by the deviation of dual inlet air temperature measuring points. Based on this, a treatment plan is formulated and implemented, finally realizing the stable operation of the A coal mill and providing technical reference for coal mill fault treatment in the same type of units.