Leaching and evaporating experiments were conducted to study water-nutrient controlling effect of polymer/bentonite composites. The results obtained showed that the polymer/bentonite composites were of significant ability on retaining water and nutrient, but it fully played under the condition of water sufficient supply. The composite containing 0.5 times bentonite(based on the mass of polymer) had a water conserving ability closed to that of the polymer. The composites could reduce nutrient leaching loss by reducing water loss, and could reduce K leaching loss.