Biochemical oxygen demand of 5 days (BOD 5) was a very important parameter of monitoring ofwater quality. The classical method presented some shortcomings,such as complexity, long period, requirementof high technology and not promptly reflecting the pollution levels of water body, so it was of no significance fortreatment of industrial waste water. In this paper, two rapid methods for determination of BODs, raising incubation temperature and correlative estimation method, were introduced and their advantages, such as short period and simplicity of operation were verified by experiments. Modification of classical method was of certain instructive significance for the practical application to treatment of industrial waste water and forecast of pollutionlevels of water body.