Abstract: To investigate the biodegradation of sex steroid hormones,a high efficient degrading strain ZY3 was isolated from the active sludge of sewage treatment station in a prophylactic plant,which can degrade 3methoxy-17βhydroxy-1,3,5(10),8(9)-△4-estren(named MHE),a kind of streroid hormones.Based on its morphology,physiological and biochemical characters,as well as 16S rDNA sequence analysis,this strain is identified as Raoultella sp.Experiment results show that the appropriate range of temperature and pH for strain ZY3 using MHE is 25-37℃and 9.0-11.0,respectively.The growth of strain will he restrained when the substrates concentration is more than 20mg/L.81% of degradation rate of MHE can be obtained by strain ZY3 for 72h.The existence of metal ions such as Na⁺,Mg²⁺ and Ca²⁺ can facilitate the growth of strain ZY3,and the heavy metal ions including Sn²⁺,Mn²⁺ and Cd²⁺ can restrain its growth.The strain can utilize the estrogenic compounds easily as its sole carbon source,but can not utilize the other PAHs such as phenol,anthracene and naphthalene.