Extensive amounts of corrosion products were found on all surfaces of a large ironpot unearthed from the Sizhou City site. By XRF analysis, iron metallographic analysis and Raman spectroscopy, it was found that the iron pot was made of gray cast iron, and that the main corrosion products were Fe₂O₃, Fe₃O₄ and γFeOOH. Due to unstable environmental conditions, the iron pot is still rusting. At the site, several measures are adapted to protect the iron pot, such as cleaning the corrosion, to brush phosphating liquid to stop rusting and to seal the surface by microcrystalline wax. The iron pot was in a stable condition after treatment, and there is no more corrosion. These field conservation measures provide a reference for the conservation of large unearthed archaeological relics