Abstract: Allelopathy resulted from litter decomposition is a unique regulating mechanism and competitive effect to natural pasture. The aqueous extract from the litters of Stipa bungeana、Lespedeza davurica、and Artemisia capillaries growing in the transition region of Loess Plateau was used to investigate their effectiveness on alfalfa seedlings by measuring seed germination, plant height, shoot dry matter and root dry matter. The results of this study indicated that the three dominant plants affected the growth of alfalfa seedling, the extent of which changed accordingly with different mass fraction. The greatest inhibition effect on the seed germination and plant height of alfalfa was found in the aqueous extract from S.bungeana and A.capillaries, respectively. The inhibition effect on root dry matter of alfalfa seedlings are common in all three plants and would enhance with the reduction of mass fraction.