Abstract: The effects of extracts from A. frigida Willd. on the plant morphological indices of 3 grass species by was studied by the biological test and cultivation test. The results showed that high concentration （25 mg/mL） of methanol extract from A. frigida Willd. completely inhibited the grass growth. Most indices under the treatments of low concentration （5 mg/mL） of aqueous extract were promoted. The inhibition rates on the root length of Medicago sativa L. cv. Aergangjin and Melilotus officinalis Lam. and the stem-leaf length of Sorghum sudanense（Piper） Stapf. under the treatments of different concentrations were 18.0%~100.0%, 22.5%~30.9% and 19.7%~100.0% respectively, reaching significant or extremely significant levels. Therefore, the extracts from A. frigida Willd. had obvious allelopathic effects on the plant growth.