Abstract: The methods to acquire detection efficiency and the nondestructive assay system of barreled radioactive waste were introduced, and the changing tendencies between experimental result and theory are consistent. The verification experiments were carried through barreled radioactive materia which was made by ¹³⁷Cs standard liquor. It is indicated that relative deviation is less than 20% when radioactive sources are random distribution and medium density is less than 1.761 g/cm³, and that relative deviation is from -76% to 152% when radioactive sources are extrem distribution and medium density is 1.538 g/cm³. Calculation results show that this method is reasonable to class barreled radioactive waste from decommissioning.