Environmental impact assessment(EIA) is one of the most important policy measures for the conservation and sustainable use of biodiversity. While assessment methods for flora and fauna are being continuously developed, there has not been proper methodology set up for species needing protection such as endangered species. As one of the research projects on EIA methodology for flora and fauna, this research aims to categorize vascular plants, identify threatened species among them, and come up with systematic screening methods. The results of this research can be summarized as follows. First, this research proposes the definition of "threatened plant species" and sets the boundary of threatened species subject to EIA. Second, it compares and analyses the EIA regulations and the actual practices. In the process, a number of discrepancies between them are identified and improvement measures are proposed. Third, this research selects 227 plant species as threatened species through a thorough literature review and expert consultation. Fourth, 10 screening criteria are suggested in this research with reference to threatened species lists such as the IUCN Red List. The 10 selection criteria are A) importance as Korean endemic species, B) geographic range, C) number of populations, D) population size, E) habitat stability, F) extinction status outside Korea, G) population reduction, H) habitat diversity, I) human use, J) symbolism of the species and possibility of resident’s cooperation in conservation. Fifth, detailed improvement measures for each EIA step are suggested. Last, the appendices provide a list of 227 threatened species and taxonomic and ecological information on 64 endangered plant species designated by the Wildlife Protection Act. This research is significant in that it suggests a set of screening criteria for vascular plants to categorize them into four groups requiring different levels of protection and seeks ways to use the categorization in conducting EIA. In line with this research, there should be more research on mammals, birds, amphibians, and insects that are also very important for evaluating biodiversity-related EIA issues.