Polyethylenimine(PEI)-modified magnetic hydrogel nanocomposite absorbents (PEI-mHNAs) were fabricated based on poly(acrylamide-co-acrylic acid) and PEI-modified magnetic nanoparticles by radical copolymerization. FTIR and XRD results preliminarily confirmed the target structure of PEI-mHNAs without destroying the structure of magnetic nanoparticles during modification and radical copolymerization. PEI-mHNAs with many rough porous and interstitial structure had high adsorption capacity of Cu(II) (217mg/g), Cd(II) (232mg/g) and Pb(II) (459mg/g). PEI-mHNAs had the best absorption capacity for heavy metal ions in the synthesis condition of acrylic acid/acrylamide mass ratio of 60 : 40, 0.8% initiator, AA neutralization degree of 70%, 0.75% crosslinker, and 15% PEImodified magnetic nanoparticles. Moreover, PEI-mHNAs had good magnetic responsiveness, high thermal stability and reusability, which make it a potential application in removing heavy metal ions from the contaminated wastewater.