The iodide in samples was oxidized to iodate by bromine water, which could be removed by formic acid, and iodate could be transformed to I-3 with excess of I- in phosphoric acid, the iodate in samples could be transformed directly to I-3 with excess of I- in phosphoric acid. The I-3 solution had strong absorption at 350 and 288 nm, and the absorbance had a linear relationship to the concentration of I-3 in a certain range. Total content of iodide and iodate had been detected after samples were oxidized by bromine water and the content of iodate had been detected directly, and the content of iodide was obtained by difference of the two results. Based on this, the method had been established to detect iodide and iodate in brine and seafood simultaneously by ultraviolet absorption spectrometry. The volumes of bromine water, formic acid, phosphoric acid and potassium iodide had been optimized. The effect of illumination, temperature and time also had been discussed. The optional reagents condition for iodide was: 2 drops of 3% bromine water, 0.5 mL of 10% formic acid, 4 mL of 20% phosphoric acid and 1 mL of 100 g·L-1 KI. The optional reagents condition for iodate was: 0.2 mL of 20% phosphoric acid and 1 mL of 100 g·L-1 KI. The absorbance were determined after reacting for 30 min at room temperature and natural light conditions. Under the optimized conditions, the concentration of iodide and iodate in the range of 0～1.2 and 0～1.5 mg·L-1 were well agreed with Lambert Beer law. The sample blank was detected for twelve times and the detection limit of iodide and iodate were 1.54 and 14.8 μg·L-1 respectively. The RSD of twelve times determination of 0.8 mg·L-1 of iodide and iodate were 0.097% and 0.067%, respectively. The iodide and iodate in Zhabuye brine, Hong Feng underground brine, kelp, seaweed and sea cabbage had been detected, the recovery experiments also had been conducted at the same time, the recovery of iodide and iodate were between 80%～120%. All the results met the requirement of analytical chemistry.