The invention provides GA / Fe2+ nanoparticles, composite nanoparticles thereof, preparation and application. The GA / Fe2+ nanoparticles comprise or are obtained by compounding the following raw materials: Fe2+ salt, PVP and GA. ZIF-8 is adopted to encapsulate the GA / Fe2+ nanoparticles and carry drugs such as DOX and / or GOX to obtain the composite nanoparticles, the content of iron ions in tumor cells can be remarkably increased, meanwhile, in combination with the carried drugs, a synergistic effect on tumor killing is achieved, a Fenton reaction is promoted, tumor cell iron death is induced, andtherefore, growth of the tumor cells is effectively inhibited.