The invention relates to a method for removing heavy metals in a water body, which is characterized in that common oxidizers for water treatment, such as hydrogen peroxide, sodium hypochlorite, potassium permanganate and the like, are utilized for oxidization to activate the zero-valent iron surface and continuously generate fresh iron (III) / (II) (hydro)oxide and other active components, thereby quickly and efficiently removing heavy metals in the water body, including As, Hg, Cd, Pb, Cr, Se, Sb, Cu, Zn and the like, in a mode of adsorption, precipitation, redox or the like.