Abstract: In the natural environment, there are often herbaceous vascular plants around the Brachythecium pulchellum, and these herbs are often spontaneous autogenous plants. In order to investigate the influence of Brachythecium pulchellum on the growth of adjacent symbiotic autogenous plants or the possible allelopathic effects on them. With Brachythecium pulchellum as the test material, Trifolium repens L. and Taraxacum mongolicum Hand.-Mazz. as the recipient plants, the effects of water extracts of different concentrations（5 g/L, 10 g/L, 25 g/L, 50 g/L, 100 g/L） on seed germination and seedling growth of recipient plants were compared by indoor culture combined with bioassay. The effects of germination rate, germination potential, root length, seedling height, root vigor, chlorophyll content and allelopathy index on seed germination, seedling growth and physiological indexes of recipient plants were analyzed and evaluated. The results showed that the germination rate and germination potential of the two plants were "promoted by low concentration and inhibited by high concentration", and the root activity and chlorophyll content were promoted in the treatment group. The root activity values of the Taraxacum mongolicum treatment groups were higher than the control group. Water extract significantly inhibited the growth of seedling roots, but promoted the growth of seedling shoots, and the inhibition and promotion effects became stronger with the increase of water extract concentration; When the water extract concentration was 100 g/L, the root length of Trifolium repens L. and Taraxacum mongolicum Hand-.Mazz. were 33.8% and 37.0%（p＜0.05） of ck, and the seedling height was 212.8% and 188.9%（p＜0.05） of ck, respectively. The allelopathy index of seedling height and root activity of the two plants were positive, indicating that the water extract of Brachythecium pulchellum promoted the allelopathy of the two plants. The root length allelopathy index was negative, which indicated that it was allelopathy inhibition. In conclusion, there were different types and degrees of allelopathic effects on seed germination and seedling growth of Trifolium repens L. and Taraxacum mongolicum Hand.-Mazz. in the water extract, which showed promoting effect on the whole.