Abstract: To investigate the allelopathy of Mikania micrantha H.B.K. (M. micrantha), a pot experiment was conducted to study the effects of leaf leachates of M. micrantha at different concentrations on rhizosphere soil potassium activation and soil enzyme activity of M. micrantha and the co-occurring plant, Polygonum chinense (P. chinense). The results showed that leaf leachates of M. micrantha increased the activity of dehydrogenase and β-glucosidase in rhizosphere soil of M. micrantha. And in M. micrantha monoculture, available potassium content in rhizosphere soil was 2.53 times higher than those of the control (0 g/L), when the leaf leachates concentration of M. micrantha was 15.00 g/L. In the meanwhile, leaf leachates of M. micrantha also increased the activity of dehydrogenase and β-glucosidase in rhizosphere soil of P. chinense. And in P. chinense monoculture, available potassium in rhizosphere soil increased by 2.03 times, and the aboveground biomass and the potassium of aboveground biomass decreased significantly at 15.00 g/L leaf leachates of M. micrantha. Our results suggested that allelochemicals of leaf leachates of M. micrantha could enhance the activity of soil enzymes and accelerate the activation of soil nutrient. But allelochemicals in leaf leachates of M. micrantha may inhibit the growth of P. chinense. The results may indicate that the allelopathy of M. micrantha plays an important role in its invasion.