Through nitrogen shock loading and organic shock loading experiments, we studied the changing rule and activity status of biological activity of activated sludge in organic matter biodegradation, nitrification and denitrification course in SBR process by the determination of INT-ETS activity. The experimental results show that INT-ETS activity could provide a good indication of the ongoing biological reactions of SBR process. Biological activity of organic matter biodegradation, nitrification and denitrification course in SBR process reduced orderly. INT-ETS activity reduced from 232.59 mg/(gxh) to 190.65 mg/(gxh) and resultly to 113.88 mg/(gxh) when the effluent concentration of COD and NH4(+)-N were 300 mg/L and 40 mg/L. Nitrogen shock loading (14.5 mg/L and 42.0 mg/L) and organic shock loading (COD are 293 mg/L and 685 mg/L) experiments cure verify that the operational conditions could not influence the changing rule of INT-ETS activity, but the time of the appearance of break points marking different reaction course in profile was influenced.