Abstract: The effect of reaction time, concentration of bactericides (isothiazolone and 1227), corrosion and scale inhibitor (ATMP) on the efficiency of intermittent activated sludge treatment system was investigated by a batch activated sludge reactor. Results showed that the existence of such water treatment agents in simulated wastewater could decrease the COD removal rate, NH3-N removal rate and oxygen consumption rate of the system, as well as inhibit the growth of heterotrophic bacteria. On the whole, the influence of residual water treatment agents on the biochemical treating effect of intermittent activated sludge treatment system was related with the types of chemical agent, its concentration and reaction time.