Chemical oxygen demand (COD) and biochemical oxygen demand (BOD) with irreplaceable significance are comprehensive indicators for evaluating water quality. Effective control of water pollution depends on the rapid determination of these indicators. In the study, the rapid determination of BOD was carried out by activated sludge aeration degradation method. The BOD quantification was achieved by measuring the COD change before and after microbial degradation (BOD_ΔCOD). Singlefactor experiment was employed to investigate the effect of operating parameters on the determination of BOD. In addition, the interactions of main variables were evaluated by Box-Behnken Design, and the results showed that the interaction term of reaction time and initial pH value had a significant effect. The optimum conditions for determination of BOD were reaction time of 273.68 min, dosage of activated sludge of 8.72 mL, and pH of 7.18. Under the optimal conditions, the correlation experiment showed that BOD_ΔCOD and BOD₅ exhibited a good linear relationship in the concentration range of 0-500 mg/L, and the correlation coefficient R² was 0.996. It indicated that the method realized not only the rapid determination of BOD, but also the integrated determination of COD and BOD.