The invention discloses a pre-oxidation furnace. The pre-oxidation furnace comprises a furnace body shell, a roller, a circulating fan and an exhaust fan, wherein the circulating fan and the exhaust fan are connected with the furnace body shell by virtue of connecting pipelines, two ends of the furnace body shell are provided with furnace end humidifying devices, a humidifying
pipe is arranged inside each furnace end humidifying device, a humidifying hole is formed in the humidifying
pipe, and each humidifying
pipe is connected with a humidifying
liquid storage tank by virtue of a connecting pipeline. Two ends of the pre-oxidation furnace are provided with the furnace end humidifying devices, so that in the pre-oxidation production process, the
mechanical abrasion and damage of
carbon fibers can be greatly reduced, the quantity of broken filaments on the surface of the
carbon fibers can be greatly reduced, a pre-oxidized filament obtained by pre-oxidizing carbon
fiber crude filaments by virtue of the pre-oxidation furnace basically has no
skin-core structure or has a slightly
skin-core structure, the tensile strength and the tensile
elastic modulus of the
carbon fibers prepared by carbonizing the pre-oxidized filament are greatly improved, and the carbon fibers are not prone to break.