Abstract: In view of the problems of long process, high reagent cost, and insufficient A/O denitrification capacity in the existing phosphogypsum leachate treatment process, a full chemical treatment process based on precipitation phosphorus and fluorine removal, reduction of nitrate nitrogen and oxidation ammonia nitrogen removal was designed. The effects of factors such as lime milk dosage, pH, oxidant dosage, and flocculant on the removal efficiency of phosphorus, fluorine, ammonia nitrogen, and total nitrogen were investigated. The parameters of the pilot scale experiment were optimized, and the execution effect of the process running continuously for 2 months was evaluated. The results show that under the action of iron based composite materials, the reduction rate of nitrate nitrogen is as high as 67%, while ammonia nitrogen can be completely oxidized by subsequent sodium hypochlorite under neutral conditions. In addition, the average concentrations of total phosphorus and fluoride ions in the leachate after secondary lime milk precipitation remain stable around 0.37, 1.50 mg•L⁻¹ respectively. The process has the characteristics of low investment, short process, high efficiency, fast speed and low reagent consumption. The effluent indicators meet the standard of DB 34/2710—2016, which can provide new ideas for the treatment of same type of phosphogypsum leachate up to standard.