The utility model relates to a steam-passing siphon type drying roller which is used on a drafting device of polyacrylonitrile-based (PAN-based) carbon fibers and plays the function of drying the carbon fibers. The drying roller is formed by a rotating connector, a steam inlet and outlet loop system, a rotating joint installation sleeve, a main shaft, a jacket type roller, a siphon type condensate water clearing device and a postprocessing steam-water separation device. The steam-passing siphon type drying roller adopts the structure of a rotary type siphon, double pipe loops and the jacket type roller, and achieves the inlet and outlet circulation of the steam and the separation of water and steam. Compared with a single roller and a fixed siphon structure of current textile industry and the other industries, the structure of the steam-passing siphon type drying roller has the advantages of being little in steam quantity passing a cylinder, little in condensate water, prone to discharging the condensate water, strong in tightness, little in leakage, fast in temperature rising, even in temperature field, and high in safety. Compared with other drying rollers, the steam-passing siphon type drying roller further has the advantages of being compact in structure, simple and practical, strong in manufacturability, and meeting the using requirements of a production line.