The invention discloses a pressurized steam pipe type drafting device and method for production of polyacrylonitrile filaments for carbon fibers. The device comprises a steam guide-in system, a steam condensation system, a chamber, drafting drivers, a drafting cavity, seal cavities and exhaust pressure reduction cavities. The drafting drivers are arranged on two sides of the chamber, and the seal cavities and the exhaust pressure reduction cavities are sequentially arranged on two sides of the drafting cavity in the middle of the chamber. A plurality of groups of abreast air inlet pipes in the middle and pre-heating pipes and drafting pipes on two sides of the air inlet pipes are arranged in the drafting cavity. The steam guide-in system guides saturated steam into the air inlet pipes, the exhaust pressure reduction cavity discharges saturated steam into the steam condensation system, and strands are drafted in from the exhaust pressure reduction cavity on one side of the chamber by the drafting drivers and sequentially pass through one seal cavity, the pre-heating pipes, the air inlet pipes, the drafting pipes and the other seal cavity to get out from the exhaust pressure reduction cavity on the other side of the chamber. The pressurized steam pipe type drafting device and method have advantages that high-speed continuous spinning is realized while high strength, compactness and fine denier of filaments are realized, and fiber uniformity is guaranteed.