The invention belongs to the field of roller structures of open mills or calendaring machines, and discloses a bi-directional temperature-controlling roller of an open mill or calendaring machine. The roller comprises a roller body, end covers which are installed at the two ends of the roller body and provided with track grooves and a plurality of temperature-controlling through holes formed in the roller body, and the temperature-controlling through holes are communicated through the track grooves of the end covers in a spaced mode to form two snake-shaped through holes. According to the roller, a medium flows bi-directionally and is fully distributed on the surface of the whole roller, therefore, uniform heating or cooling of the working surface of the roller body of the open mill or calendaring machine is guaranteed, the problems that the roller temperature difference is large, and temperature controlling is not uniform are solved, and the heating or cooling effect of the roller is improved; the quantity of the through holes is small, the structure is simple, and therefore it is guaranteed that the roller has the enough mechanical strength and rigidity; on the premise that the mechanical strength is guaranteed, the roller can control the flow of the medium by changing the pipe diameter of a liquid inlet pipe, the size of through holes and the size of a medium inlet and a medium outlet, and then the heating or cooling effect is influenced.