Abstract: An analytical method performed by solid-phase extraction(SPE) system with high pressure liquid chromatography and tandem mass spectrometry(HPLC/MS/MS) was developed for validating the efficiency of the triplet loop airlift biofilm reactor(TLABR).The steroid estrogens,including estrone(E1),17β-estradiol(E2),estriol (E3) and 17α-ethynylestradiol(EE2),of influent and effluent of the bioreactor were determined by this method.The average recoveries ranged from 88% to 103% and the precision of the method ranged from 4% to 9%.The limit of quantification(LOQ) was determined at 0.7 ng/L for E1,0.8 ng/L for E2,0.9 ng/L for E3,and 0.5 ng/L for EE2 in influent,and 1.0 ng/L for E2 and EE2,and 2.0 ng/L for E1 and E3 in effluent.The effluent could still remain stable,when the influent volume load of COD_Cr and NH3-N reached as high as 7.5 and 1.6 kg/(m³·d) respectively.The influent pH was generally kept at 9.0 ～10.5,and the pH within the reactor remained stable at below 9.0.Therefore,the system could adapt to the impact of pH.Also,stable accumulation of NO2——N was formed in the reactor,and the removal rates of COD_Cr and ammonia reached 70% and 73%,respectively.