The invention discloses an air duct cooling system of a zone A of a rolled glass annealing lehr. The system comprises a zone A1 cooling device, a zone A2 cooling device and a fan air supply system; the zone A1 cooling device comprises a plurality of first upper cooling air ducts, a plurality of first lower cooling air ducts, a zone A1 external main air duct, a plurality of first upper control valves, a plurality of first lower control valves, a plurality of first upper temperature measuring elements and a plurality of first lower temperature measuring elements; the zone A2 cooling device comprises a plurality of second upper cooling air ducts, a plurality of second lower cooling air ducts, a zone A2 external main air duct, a plurality of second upper control valves, a plurality of second lower control valves, a plurality of second upper temperature measuring elements and a plurality of second lower temperature measuring elements; the fan air supply system comprises an air supply main pipe, a first fan, a second fan, a first main pipe control valve, a second main pipe control valve and a third main pipe control valve. The air duct cooling system improves the cooling effect on the zone A and reduces the energy consumption of the zone A and the cost.