The ecological and economic impacts of exotic invasive weeds have been followed with interest. A successful invasion of exotic weeds depends not only on their bio-ecological traits, but also on some specific mechanisms of invasion. The clarification of the invasive mechanism of exotic weeds will be beneficial to predict and manage on them. In the process of establishment, reproduction and spreading, an exotic species has to become dominant in the interactions with native ones at new habitats, and then invades successfully. Among invasive mechanisms, the chemical interaction between exotic and native weeds should not be neglected. Previous studies showed that allelopathy plays an important role in exotic weed invasion. In fact, plants are able to defend or inhibit animals, plants and microbes from new habitats by using some specific chemicals. The chemical mechanism of exotic weed invasion might involve each aspect of plant chemical ecology. Therefore, chemical ecological characteristics of exotic weeds should be regarded as one of the most significant factors on predicting invasive species. The studies on chemical mechanism of exotic weed invasion will be one of the important aspects in future.