Abstract: Different solvents including cyclohexane, ethyl acetate, n-butanol and XAD-4 resin were used to extract the allelochemicals from the decomposing products of soybean stubs. The results showed that the germination of soybean seeds were inhibited at initial stages by the solution extracted with cyclohexane, ethyl acetate,n-butanol and resin from the decomposing products of soybean stubs that had been incubated for 2 and 4 weeks. The inhibition was gradually weakened with the time. When concentrations of the ethyl acetate and resin fractions were 0.50, 1.00gDW穖l^-1and when their concentrations were 0.10, 0.25gDW穖l^-1,their RI (the index of allelopathic effect) value of soybean radicle length reached significant level. The RIvalues of the former and those of the cyclohexane fractions reached significant level also. The chemical constituents of allelopathic fractions were identified by GC-MSas organic acids, phenol, aldehyde, ketone, benzene, amine, nitrile, ester and some other compounds, some of which were allelochemicals.