The invention discloses a large-filament bundle multi-spinning position polyacrylonitrile fiber steam pressurizing and traction apparatus and a method for the same. The traction apparatus comprises a traction cavity, decompressing cavities, pre-heating cavities, silencing cavities, condensed water discharging ports, exhaust ports and a parameter control system, wherein a multi-stage ceramic sealing device is disposed in each decompressing cavity. The method is characterized in that fiber filament bundles enter spinning channels via spinning inlets of the traction apparatus, then pass through the silencing cavities, the pre-heating cavities and the decompressing cavities until extending into the traction cavity; water vapor pressure in the spinning channels increases along a spinning direction in a ladder way; traction temperature increases in a ladder way, so the large-filament bundle fibers can be pre-heated first, then compressed in the traction area via the decompressing cavities; when the large-filament bundle fibers pass through the decompressing cavities, the pre-heating cavities and the silencing cavities on the other end, high magnification traction can be achieved. The large-filament bundle multi-spinning position polyacrylonitrile fibers can be drafted in a high magnification and even way in high-pressure water vapor; fiber orientation degree can be improved; and lousiness and wool balls can be reduced and even avoided.