Abstract: To determine the weed-inhibited effect of characteristic plateau plants, the effects of seed germination and seedling growth of five characteristic plateau plants were studied by biological detection method in laboratory. The results showed that the water extracts of five plateau plants had a certain inhibitory effect on the seed germination and seedling growth of the two kinds of weed seeds, and the effect increased with the increase of the mass concentration. And, the inhibition rates of seed germination, root length and bud length of the two kinds of weed seeds reached 100% while the concentration Mellilotus officinalis water extract was above 5 mg·mL^-1. Therefore, the M. officinalis could be regarded as a key candidate for the development of botanical pesticides.