This study was conducted to develop the new Environmental Impact Assessment techniques for the grading of rareness in plant. 17 EISs which were submitted in 1996 were analyzed to know the problems in existent EIA techniques for the conservation of rare plants. Category of rare plant was reevaluated and evaluation technique for the grading of rareness in plant was developed. The results obtained from this study were as follows: 1. The evaluation technique of rareness in plant was not reflected in the current preparation provision for EIS. And t his fact also appeared in most of the EIS which were reexamined in this study. 2. The category of rare species which have been considered as the subject of protection in EIA have to be enlarged to more than legally protected species designated by MOE. 3. The taxonomic characteristics and status of species, characteristics of population, geographical characters, extent of threat and its possibility by man resulted from the habitat loss were investigated. Each item was endowed scores from 1 to 5 and all the scores were summed, and then this value was used to evaluate the order of conservation. 4. Conservation measures for the rare plants have to be applied according to the levels of rareness grade, and they are absolute conservation, in situ conservation, transplanting and ex situ conservation, post observation and none by the levels from A to E. 5. Considering the phenology of rare plants, investigation for the rare plants have to be made a1 least three times. 6. Size of the MVP(Minimum Viable Population), pollination ecology also have to be considered for the conservation of rare plants. And in the case of adopting ex situ conservation measure, the site and methods for the conservation of rare plants have to be proposed in detail.