The invention discloses a low-NOx mixed burning system and method with coupling of a pyrolyzing furnace and a pulverized coal boiler. The low-NOx mixed burning system comprises a coal pyrolyzing system formed by a raw coal cabin, a drying device, a coal pyrolyzing furnace, a semicoke collection device, a pyrolysis dust removal device and the like and a mixed burning system of pyrolyzing semicoke and bituminous coal; and the mixed burning system of pyrolyzing the semicoke and the bituminous coal is formed by a semicoke small material cabin, a coal mill, a desulfurization device and the like. For the low-NOx mixed burning system and method with coupling of the pyrolyzing furnace and the pulverized coal boiler, by putting the pyrolyzing furnace in front of the pulverized coal boiler, a semicoke large material and a semicoke small material obtained by pyrolyzing are separately stored and utilized, the semicoke large material is used as a chemical product, the semicoke small material is used as burning and bituminous coal for layering mixed burning, and a part of pyrolysis gas is used as a reburning fuel for a boiler to be sprayed into a furnace hearth for reburning. The low-NOx mixed burning system and method with coupling of the pyrolyzing furnace and the pulverized coal boiler lower production of NOx while solving resource waste of the semicoke small material and the pyrolysis gas and the various problems in the burning process, realizes full utilization of energy, is economic and environmentally friendly without improving the existing pulverized coal furnace, is wide in adaptability range and has a wide application prospect.