The invention relates to a method for removing heavy metal cadmium and lead pollutants in water by sodium alginate/gelatin coated nano zero-valent iron. By using sodium alginate/gelatin as a main raw material and CaCl2 as a crosslinking agent, the nano zero-valent iron is synergically immobilized. Researches show that the nano zero-valent iron has very high stability and researches on the effect of removing heavy metal ions Cd<2+> and Pb<2+> show that the zero-valent iron has a relatively good removal effect which can reach over 95%. The immobilized nano zero-valent iron prepared by the invention has the advantages of being green and environmental-friendly, has relatively high reaction activity and stability, and has a relatively good removal effect on heavy metal ions both Cd<2+> and Pb<2+>.