To reveal the reason for the structure of an Artemisia sacrorum community at the stage of "Grain for Green" vegetation restoration on the hilly-gully region of the Loess Plateau and to disclose the association between plant community and allelopathy, this work studied the impact of extracts by water and methanol solution from A. sacrorum (restoration for 10, 15, 20, 30 years) on seed germination and seedling growth of accompanying species, including Lespedeza davurica, Artemisia capillaries, and Setaria viridi, as well as A. sacrorum, based on seed germination experiment. The results showed that extracts from A. sacrorum had a significant (P < 0.05) influences on the germination of seeds for the companion species, which were characterized by low concentrations of extract for promotion or slight inhibition and high concentrations for strong inhibition for the seed germination of the three accompanying species. The growth of the roots was more inhibited by the extract than the shoot. Seed germination and seedling growth of A. capillaries was completely inhibited at the 0.1 g/mL aboveground extract, with the -1.00 of RI. Extracts from roots and aboveground parts of A. sacrorum exerted different inhibition on the seed germination and seedling growth of L. davurica, A. capillaries, and A. sacrorum, and the inhibiting effects at the same concentration increased with the restoration time. Extracts from the rhizosphere soil of A. sacrorum generally promoted seed germination of three plants, but inhibited seedling growth of L. davurica, A. capillaries, and A. sacrorum, characterized by high concentrations (0.1 g/mL) of extracts for strong inhibition for its seed germination and seeding growth. Our findings indicated that allelopathy plays an essential role in the formation of the vegetative community, which is an important factor for A. sacrorum to be dominant in the community at stage of "Grain for Green" vegetation restoration on the hilly-gully region of the Loess Plateau.