In this work, the allelopathic effects of invasive Mikania micrantha on seed germination and seedling growth of Bidens pilosa was assessed. The results showed that after treated with extracted fluid from M. micrantha, the germination percentage of B. pilosa is 52% in non-invaded habitats, but the germination percentage of B. pilosa is 60% in invaded habitats which showing that the allelopathic effects of M. micrantha on seed germination of B. pilosa in non-invaded habitats was greater than those in the invaded habitats. M. micrantha showed no significant suppression effect on total leaf area, maximum quantum yield and shoot weight of the seedlings of B. pilosa. The root weight of B. pilosa seedlings from non-invaded habitats treated with M. micrantha and the control habitats was 23.50 g and 36.92 g respectively which was 22.19 g and 16.53 g with B. pilosa seedlings respectively from invaded habitats treated with M. micrantha and the control habitats, which showed that the effect of M. micrantha on root weight of B. pilosa seedlings in non-invaded habitats was greater than that in invaded habitats. The result indicated that both the seeds and the seedlings of B. pilosa in invaded habitats had developed allelopathic-resistance to M. micrantha.