Abstract:In the investigation of vegetation with invasive weed Mikania micrantha, 81 sample plots with10 m×10 m each were used to study the plant species, breast height diameter, crown diameter, slope and aspect, and the importance value of each species. The corresponding data obtained from original or secondary forest vegetation were used for comparison. Ecological-economic loss was analysed by methods of market valuations, shadow engineering, opportunity cost, and substitute expense. It is estimated that the economic loss amounts to 4.5-10.13 million yuan for the whole island.