In order to improve the efficiency of the activated carbon-activated persulfate process for organic wastewater,Ni /GAC catalyst was prepared by loading nickel on granular activated carbon ( GAC) via an impregnation- calcination process.Then,the catalyst was characterized by means of SEM,FT-IR and XPS,and the effects of sodium persulfate ( PDS) dosage,Ni /GAC dosage and pH value on the degradation of acid orange 7 ( AO7) by PDS activated with Ni /GAC were investigated.Finally,some main oxide radical species existing in the reaction system were discussed.The results show that ( 1) after the impregnation-calcination process,the Ni specie loading on the catalyst is NiO,and there are much more carboxyl,lactone and phenolic hydroxyl groups on Ni /GAC catalyst surface,so that the catalyst is of high catalytic activity; ( 2) with the increase of PDS dosage,the removal of AO7 first increases and then decreases; ( 3) the catalytic degradation effect on AO7 increases with the increase in Ni /GAC dosage; ( 4) the catalytic degradation efficiency decreases when the pH value changes from neutral to alkaline and then to acidic; and ( 5) in the optimal reaction conditions,namely,a PDS dosage of 2 mmol /L,a Ni / GAC dosage of 2 g and a pH value of 7,93.9% of AO7 can be removed in 90 min.In addition,it is found that hydroxyl radical ( HO·) and sulfate radical ( SO₄^- ·) are two main oxidizing substances of the catalytic system.