The invention relates to the technical field of construction of building pipelines and channels, in particular to an air-conditioning air pipe reconstructed through an industrial smoke discharging pipeline and a construction method thereof. The problems that according to an existing old factory building reconstruction engineering, an original industrial style cannot be reserved or subjected to effective reconstruction and reuse are solved. The air-conditioning air pipe reconstructed through the industrial smoke discharging pipeline is formed by connecting of a plurality of air-conditioning air pipe standard knots in head-to-tail and bolted mode. An inner heat-preservation layer is laid onto an inner cavity of an air-conditioning air pipe. Each air-conditioning air pipe standard knot comprises an air-conditioning air pipe blank manufactured after the industrial smoke discharging pipeline is treated, a sealing part arranged at a hole of a three-way connector of each pipe blank and a plurality of air-conditioning nozzles installed on each pipe blank. The construction method comprises the steps that the air-conditioning air pipe blanks are obtained by treating the surface of the industrial smoke discharging pipeline, the holes of the three-way connectors of the pipe blanks are sealed, air-conditioning nozzle short pipe bodies are installed on the pipe blanks, and air-conditioning air pipe is formed by connecting the multiple pipe blanks in head-to-tail and bolted mode; and the inner heat-preservation layer is laid onto the inner cavity of an air-conditioning air pipe, and the air-conditioning nozzles are installed on the air-conditioning nozzle short pipe bodies.