In order to improve the accuracy of the volumetric method for the determination of iodine content in brine,the determination of iodine content by saturated bromine water method was evaluated.The source of uncertainty was summarized from three aspects,such as the preparation of potassium iodate standard solution,calibration of Na₂S₂O₃ standard solution and brine sample determination.The detailed evaluation process of uncertainty components in measurement of iodine content in brine was given by establishing mathematics model.Synthesis standard uncertainty and expanded uncertainty of iodine content were obtained by the uncertainty components.The uncertainty of measurement of iodine content in brine was 17.52±0.116 mg/L in the level of 95% confidence level.