The invention discloses a boiler fire detection cooling air system and control logic thereof. The system comprises a fire detection cooling fan A, a fire detection cooling fan B, a tee joint, a fire detection cooling air main pipe, a primary air main pipe, a pressure switch A, a pressure switch B, a pressure switch C, a pressure switch D, a pressure gauge A, a pressure transmitter, a pressure gauge B, a differential pressure switch A, a differential pressure switch B, a differential pressure switch C, a fire detection cooling air A layer main pipe, a fire detection cooling air B layer main pipe, a fire detection cooling air C layer main pipe, a fire detection cooling air D layer main pipe, a fire detection cooling air E layer main pipe and a fire detection cooling air F layer main pipe; and the control logic comprises a boiler MFT logic diagram, a fire detection cooling fan A and fire detection cooling fan B input logic, a fire detection cooling fan A stop logic and a fire detection cooling fan B stop logic which is caused by the fire detection cooling air system. The system and the logic have the beneficial effects that an air source of the primary air main pipe serves as a main air source, the pressure switches, the pressure gauges, the differential pressure switches, the pressure transmitter and the like are utilized to cooperate with the control logic and to monitor the whole system, the stability of the boiler fire detection cooling air system is greatly improved, and the risk of the boiler MFT caused by faults of the fire detection cooling fan of a unit is reduced.