In order to obtain better product performance in steel production process，it is necessary to use hydrochloric acid for rinsing or soaking.A large amount of corrosive and polluting waste liquor will be produced after pickling，and the direct discharge of acid pickling waste liquor will cause serious environmental pollution.Aiming at the waste liquor，hydrogen peroxidewas added to the waste liquid for oxidation，and polymeric ferric chloride was prepared.The optimal treatment process was found to achieve the purpose of resource recovery and environmental harmlessness.KH2PO4 as stabilizer could make polymer?鄄ic ferric chloride more stable.When n（P）/n（Fe） in solution was 0.048 6，the product of polymeric ferric chloride did not precipi?鄄tate for a month.The mass fraction of iron in the finished product of polymeric ferric chloride was 11.04% and the salinity was 10.2%， which met the requirements of the standard HG/T 4672—2014 for water treatment agent polymeric ferric chloride.