Abstract: A potentiomtric titration method for the determinatio for the determination of free acid in simulated high level liquid wste is ddscribed. The test sample is directly titrated under the mask of hydrolizable ions, such as Fe³⁺, Al³⁺ and Nd³⁺, with 8% potassium oxalate. The relative standard deviation of analysis is 1.8% and the recovery is 100-101%. This method is simple,rapid and accurate, and can be used to provide analytical data for the solidification resarch or radioactive waste.