Abstract: The early warning of activated sludge inhibitory rate by Cu2 + ，Zn2 + was studied based on oxygen uptake rate ( OUR) index． When dosage of Cu2 + and Zn2 + increased from 20 mg /L to 60 mg /L， the OUR inhibitory rate increased from 33% and 38% up to 77% and 63%，respectively． With a rising of dosage of heavy metals，the activated sludge's inhibitory rate measured by OUR index was enhanced． With a certain condition and common dosage of heavy metals ( 20 mg /L) ，the OUR inhibitory rate order by four heavy metals was Cu2 + ＞ Zn2 + ＞ Cd2 + ＞ Cr3 + ． The operation parameters for early warning reactor were optimized by single factor and orthogonal test，the results indicated that the best parameters were as follows: ρ( MLSS) = 500 mg /L，HRT = 10 min． The early warning equipment was applied to simulate sewage added in Cu2 + and Zn2 + respectively，which indicated that the OUR inhibitory rate was 22. 3% and 56. 6%，with common dosage of heavy metals ( 5 mg /L) ． Thus，the early warning equipment based on oxygen uptake rate ( OUR) index can be applied to early warning of the activated sludge inhibitory action by heavy metals in wastewater treatment plant．