To prepare a kind of superabsorbent polymers by gracilaria lemaneiformis，superabsorbent polymer was synthesized by means of microwave irradiation. Acrylic acid and acrylamide were grafted onto gracilaria lemaneiformis by using potassium persulfate as an initiator in the presence of N, N′-methylenebisacrylamide (MBA) as a crosslinker. The univariate analysis was visually analyzed to choose the optimal conditions. The structure of LSAP was confirmed while the absorbing properties, swelling rate and water retention were investigated. The optimum conditions show that the mass ratio of monomer to gracilaria lemaneiformis is 2∶1, the mass amount of initiator is 0.4%, the mass amount of crosslinker is 0.06% and the microwave power is 500 W respectively. Under the optimum condition, the absorbency of LSAP is up to 1 102 g/g in deionized water, 104 g/g in NaCl and 86.1 g/g in artificial urine, respectively. The performance test of LSAP indicates that it has faster absorbent velocity and excellent water retention. 