Abstract: An indirect spectrophotometric method for determination of SO2-4 radical in polysaccharose sulfate was proposed.A definite amount of the hydrolyzed sample solution was taken and the sulfate radical was precipitated as BaSO4 by adding an excess of known amount of standard barium chloride solution.After staying for 5 min,a definite and excess amount of standard potassium chromate solution was added to the reaction mixture to precipitate the excess amount of Ba2+ as BaCrO4.The precipitate was separated by centrifuging,and an aliquot of the supernatant solution was taken to react with o-toluidine in an acetate buffer solution of pH 3.4,giving a colored product,the absorbancy of which was measured at 624 nm.Beer′s law was obeyed in the range of 50-250 μg for SO2-4.Precision and recovery of the method were tested giving results of RSD′s (n=6) to be 1.55%,and value of average recovery to be 99.25%.