The invention provides graphene/sodium alginate globules modified by nano zero-valent iron and a preparing method and application thereof.The method includes the steps that oxidized graphene prepared in advance is used for modifying sodium alginate gel, nano zero-valent iron particles are doped, and oxidized graphene/sodium alginate globules modified by nano zero-valent iron are prepared through a cross-linking and curing reaction; the graphene/sodium alginate globules modified by nano zero-valent iron are obtained through thermal reduction.The globules can be applied to reduction recovery of hexavalent chromium in water.As graphene is introduced, electron transfer between nano zero-valent iron and contaminants can be effectively promoted, globule porosity is improved, and the removal efficiency is improved.Mechanical strength of the globules is enhanced, the damage percentage of the globules in the decontamination process is reduced, and secondary pollution is reduced.Furthermore, the zero-valent iron particles partially oxidized in the embedding process are reduced again by means of thermal reduction, and therefore reactivity and treating capacity of the globules are improved.