According to the theory that 3,3′,5,5′-tetramethylbenzidine(TMB) can be oxidized under acid condition by potassium bromate (KBrO3) and the principle of color reaction, potassium bromate content in wheat flour was detected by qualitative detection of visual colorimetry and quantitative detection of spectrophotometry. The effects of system acidity, color liquid dosage, reaction time on the change of color were studied, and the experimental conditions were optimized. Results showed that under the optimal experimental conditions, the color gradually deepened as the potassium bromate content rose, and the concentration of potassium bromate within the range of 0~4 mg/L in line with the beer′s law. The linear regression equation was ΔA=0.2437 C-0.0052 with R2=0.999 3. These methods can be applied in practice, visual colorimetric method can determine the content of potassium bromate rapidly and the recovery rate of spectrophotometric method was 96.51%~101.70%, RSD 1.79%~3.12%, which can meet the needs of the supervise of food safety in the market.