Wastewater at various stages of treatment was sampled from a large wastewater treatment plant (WWTP) in Beijing, China. A fractionation method was conducted to identify the dominant contributors to estrogenic activity of those samples using silica gel column chromatography combined with a recombinant yeast bioassay for detecting estrogenic activity and gas chromatography-mass spectrometry (GC/MS) for quantifying estrogenic substances. Total estradiol equivalents (EEQ) found in the influent and effluent of the WWTP were 15.7±2.0 and 10.4±0.4ng/L, indicating the low removal efficiency of the WWTP. The endocrine disrupting chemicals (EDCs) most frequently detected in the wastewater by GC/MS included phthalate esters, PAHs and phenolic compounds, while the natural and synthetic estrogens such as estradiol (E2), estrone (E1), and ethinylestradiol (EE2) were not detected. The concentrations of nonylphenol (NP), octylphenol (OP) and bisphenol A (BPA) were 13.4, 1.4 and 89.0μg/L in the influent and 0.41, 0.11 and 0.32μg/L in the effluent, respectively. Based on the concentrations and estradiol equivalency factors (EEF) of NP, OP and BPA, 60% of the total estrogenic activity in GBD-WWTP influent could be explained by the calculated EEQ, showing that BPA, OP and NP were mainly responsible for estrogenic activity in the influent. However, their contributions to estrogenic activity in the effluent were only 3%, indicating that some unknown estrogenic components were still present in the wastewater.