Recently, iron nanoparticles have become one of the main research materials for environmental remediation due to the excellent catalytic/reduction performance, low cost and environmental friendliness. At present, the research of iron nanoparticles mainly focuses on the heavy metal removal, organic pollution degradation, inorganic anion catalytic reduction in sewage system, etc. However, there still exist some problems, such as low removal efficiency, poor stability, and single removal on account of several self-defects of agglomeration and tedious structures. Hence, this review focuses on the following aspects: 1) controllable preparation of iron nanoparticles; 2) interface design of iron composites; 3) application of iron nanoparticles in heavy metals removal and electrocatalytic denitrification; 4) prospect of iron nanoparticles composites in environmental remediation.