Abstract: To improve the cumulative release rate of iron, polyacrylic acid grafted alkali lignin-based (ALS-G-P (AA)) iron fertilizer was prepared by acrylic monomer grafted the amorphous alkali lignin. The influences on water absorbency of the materials to neutralization degree of acrylic acid, the dosage of initiator and cross-linking agent, temperature and grafting degree of alkali-lignin were investigated by orthogonal test. Release performance of ALS-G-P (AA) iron fertilizer was researched. The results showed the ideal preparation conditions were as follow: the degree of acrylic acid was 60%, amount of initiator was 0.06 g and the cross-linking agent was 0.03 g, temperature was 60℃ and alkali-lignin grafting was 25%. Water absorbency of ALS-G-P (AA) iron fertilizer was 1 017 g/g, the iron content of which was 7.74 mg/g. Effective release period of water saturated ALS-G-P (AA) iron fertilizer with was 22 days. Iron cumulative released rate of ALS-G-P (AA) iron fertilizer in water fitted a quadric equation. Curve of the iron cumulative release rate was S pattern. The study provides a reference for the efficient application of iron fertilizer, and expanded application of the alkali lignin in agricultural fields of controlled release carriers.