One of the problems of BrO3- detection using the electrochemical method, such as a cyclic voltammetry (CV) is that it is impressionable to interferences from Humic acid (HA). The objective of this study was to determine the effect of HA on electrochemical detection of BrO3- using metalloporphyrin-based multilayer sensor under different pH conditions in the presence of FeCl3. The effect of HA interference on chemical interaction at the electrode surface in the presence of FeCl3 was determined based on Fourier transform infrared spectrum. CV was used to measure the concentration of BrO3- in the solution containing HA with or without different concentrations of FeCl3. Results of CV revealed a dynamic linear concentration range of BrO3- from 10 to 100 mu g/L in 0.1 to 1 mg/L of HA solution (pH 9). The detection limit for BrO3- concentration was 8.9 mu g/L in 0.1 mg/L of HA solution.