To easily perform smooth delivery of a slurry from a tank to a solid- liquid separator (filter press) with good durability and good operability while reducing pulsation to a possible minimum, in a slurry pumping system.

In this system provided with a slurry pumping device, only a single elastic diaphragm 9 for isolating a slurry is placed in each of twin type casings 3 and 3' and also, an intermediate shock-absorbing liquid 12 that is a liquid biodegradable rust inhibitor, is interposed, as an intermediate liquid, between the elastic diaphragm 9 and a piston 11 of each of cylinders 10 and 10' which are placed in the front of the casings 3 and 3' respectively, and further, a special seal 14 made of molybdenum disulfide is fitted to the outer periphery of the piston 11 integrally with the piston 11. Further, pressure detection sensors 14 and 16' are interposed between the slurry pumping device and the side of a solid-liquid separator (filter press), to operate as delay timer, to supply the slurry with a pressure difference within a prescribed range and to prevent any water hammer, shock wave, or the like, from being caused.