A pneumatic tension control system was introduced which could be used to automatically adjust paper tension for unreeling. In this device, PLC was used to control the output pressure of the electricitycontrolled pneumatic ratio valve by getting signal level from displacement sensor. An air brake driven by this pressure was used to regulate the paper tension. In the whole production process, the paper is always kept in a constant tension state, so the phenomena of broken paper and paper yawing are eliminated.