Objective To investigate the effect of plasma exchange early on treatment for acute arsenic poisoning and prevention for acute renal failure.Methods Eleven patients of acute arsenic poisoning were treated by plasma exchange early.Their clinical features and biochemistry indexes were observed before and after treatment.Results After plasma exchange,the clinical features of all patients improved.Nine patients had normal renal function and 2 patients had impaired renal function.Conclusion Early plasma exchange is an effective measure for prevention for acute renal failure caused by acute arsenic poisoning.