Objective To explore the influence of hemodialysis(HD) and henodiafiltation on serum ?_2-microglobulin(?_2-MG) of children with acute renal failure and contrast research on declining rate of serum ?_2-MG before and after(children′s) HD and HDF.(Met-)hods By Branc Dialog HD machine of double-pump,HDF for 18 times and HD for 20 times were given to children with acute renal(fai-)lure.The serum ?_2-MG were observed before and after HD and HDF.Results A great difference was observed in level of serum ?_2-MG between before and after HD and HDF.In HDF group,there was significant difference in level of serum ?_2-MG before and after HDF(P