In a belt press of the type used to dewater heavy slurries, an improved belt drive system is provided. The upper belt is driven by at least two rollers, one of which is situated in the dewatering section wherein the upper and lower belts are squeezed and traveling together. The improved drive arrangement provides a more uniformly increasing tension in the belt as it passes through the dewatering section than in such presses heretofore. Further because the lower belt is at least partially driven by its frictional engagement with the upper belt, through the sandwiched slurry, the synchronization of the belt speeds is improved. Further improved control of the belt press performance is provided by means for sensing the speeds of the belts and responsive means for regulating the belt tensioning systems accordingly.