Abstract: Potato residue as raw material,water as solvent to synthesize carboxymethyl potato residue,Soil Water-retaining agent was synthesised by Crosslinking Agent N,N-methylenebisacrylamide and K2S2O8-NaHSO3 redox initiation system with Carboxymethyl Potato Slag Grafting Monomer Acrylic Acid and Acrylamide.The properties of liquid absorption,water retention and repeated water absorption were studied.The products were characterized by scanning electron microscopy,XRD.The results showed that the optimum conditions of the soil water-retaining agent were as follows:the mass ratio of monomer to carboxymethyl potato residue was 6∶1;the ratio of acrylamide to acrylic acid was 6∶1;the degree of neutralization of acrylic acid was 70%;the amount of crosslinking agent was 0.16%;the amount of initiator was 0.83%;product water absorption was 1 550g/g.The best product was dried in a vacuum oven for 15 h which water retention rate remained at around 68%,to centrifugal 1 h,water rate was about 74%.