In the study, the Br⁻–DPD method for the determination of IO₄⁻ concentration was established. The method facilitated the DPD indicator reaction by adding Br⁻ and DPD at pH 5.5 (50 mM phosphate buffer) to complete the measurement of the IO₄⁻ concentration. DPD⁺ could be detected by UV–visible spectrophotometer at 510 nm and 551 nm. The experimental results showed a strong linear relationship between the absorbance of DPD⁺ and the concentrations of IO₄⁻. The slopes of the calibration standard curves for absorption wavelengths at 510 nm and 551 nm are 1.92 × 10⁴ M⁻¹ cm⁻¹ (R² > 0.999) and 2.06 × 10⁴ M⁻¹ cm⁻¹ (R² > 0.999). The stoichiometric coefficient of the Br⁻–DPD method for IO₄⁻ and DPD was 1:2, and pH in the range 3.0–7.0 had no significant different on the calibration curve of the Br⁻–DPD method. The absorbance in experimental water remained stable within 600 s. The Br⁻–DPD method accurately measured trace concentration of IO₄⁻ in ultrapure water at the range of 0.05 μM–10 μM. In addition, metal ions (Fe³⁺, Cu²⁺ and Co²⁺) and common anions (SO₄²⁻, NO₃⁻ and Cl⁻) showed little interference on the Br⁻–DPD method. The results suggested that the Br⁻–DPD method is a precise and versatile approach for measuring IO₄⁻ concentration.