A novel polyacrylic acid/rice straw (PAA/RS) composite superabsorbent was prepared. The factors that can influence the water absorption of the composite were investigated, including the concentration and neutralization degree of AA, the weight ratios of N, N’-methylenebisacrylamide (MBA) to AA and RS to AA. The results show that gel effect plays a key role in the preparation of PAA/RS composite. The addition of an appropriate amount of rice straw to the composite can significantly improve the water absorption. Under the optimized condition, the water absorption of the prepared PAA/RS composite was 285.4 g/g. The composite exhibits good loading and slow-release properties for urea and is promising in agricultural and horticultural applications.