Heavy metal ion pollution has become one of the most serious environmental problems today.The development of reliable methods for the removal and determination of heavy metals in environment is of particular significance.Magnetic nanoparticles(MNPs),a new kind of nanometer-sized material,are widely used in different fields.Besides their extremely small size,high surface area,and great amount of activity sites,MNPs have the intrinsical magnetic properties which improved their unique applications in the field of separation science.Without complex centrifugation and filtration process,MNPs can be easily separated from a sample system by applying an external magnetic field.In recent years,MNPs have obtained much attention in environmental analysis,especially in treatment of heavy metal ions.In this review,the common synthetic methods developed for the preparation of MNPs,such as co-precipitation method,microemulsion method,solvothermal and thermal decomposition method are discussed.This review focuses on the applications of MNPs dealing with heavy metal ions,such as Cu(Ⅱ),Pb(Ⅱ),Cr(Ⅵ),Hg(Ⅱ),Cd(Ⅱ) and Ni(Ⅱ).Finally,the future trends and developments in this research area are prospected.