In order to explore the mechanism of yield reduction bean planted under Amorpha fruticosa,the allelopathic effect of water extracts of A.fruticosa on the seed germination and seedling growth of soybean and fababean,was investigated.The results showed that the allelopathic effect of water extracts of aerial part of A.fruticosa on soybean and fababean varied.Inhibition effect of water extracts of aerial parts of A.fruticosa on germination of soybean was stronger than that of fababean.The water extracts of A.fruticosa affected seedling height and dry weight,root length and dry weight of soybean,the synthetic inhibitory effect(SE) was in turn -12.77%,-31.35%,-27.24% and -36.76% followed with 6.25,12.5,25,50 mg/mL aerial part extracts,and the SE for fababean was 7.90%,-2.41%,-13.75% and -13.42%,respectively.The allelopathic inhibition rate increased with intense concentration of the water extracts of aerial part,with the SE being -2.44%,-16.88%,-20.75% and -25.09%,respectively.A significant increase in water soluble phenolic content,available phosphorus content and ammonium nitrogen content were recorded in soil amended with T1-T4 compared to unamended soil,and they increase with the increase of the concentration of water extracts of aerial part of A.fruticosa.However,an increase in the biomasses of soybean and/or fababean was not observed due to the increase of the concentration,the phenomenon may be allopathic effect of A.fruticosa on crop nutrient uptake.Main chemical compounds in the fraction extracted by ethyl acetate were formic acid,propionicacid,2-methyl-4-pentenoicacid,benzoicacid,3-phenylpropionicacid,4-hydroxybenzoic acid,DL-tartaric acid,cinnamic acid,4-coumaric acid,succinic acid,syringic acid,3,4-dihydroxybenzoic acid,2-methylphenol,2-methylbenzal dehyde,D-limonene,umbelliferone and 7-methoxyxoumarine