In order to evaluate 2 extensive green roof systems(Sedum Box Roof System and Roof-rainwater Utilization System) for urban greening and select ground-cover plants, which can adapt well to the drought tolerance in an extensive green roof system on 12 species. This study was carried out in order to suggest an experimental base in assessment of the Green Roof-rainwater Utilization System and selecting the drought resistance of plants. Adopting the natural drought method, this paper studies the drought resistance of 12 kinds of ground cover plants. The drought-resistance of ground cover plants subjected to dry processing time were evaluated using relative water content on leaves, relative electric conductivity and chlorophyll content in 12 kinds of plants, and the relation between soil water content under drought stress. Drought resistance of the plants were subject to rooftop drought resistance treatments. The result showed that with the increase of stress time, the relative water content and chlorophyll content on leaves were in a downward trend while the relative electric conductivity was in an upward trend. Among the 12 species of ground cover plants, excluding Pulsatilla koreana, Ainsliaea acerifolia was selected for rooftop plants because they showed resistance to drought strongly and took adaptive ability. These results showed that drought tolerance of plants in Roof-rainwater Utilization System were stronger than the Sedum Box Roof System. Therefore, the Roof-rainwater Utilization System is good for plants. It helps them adapt well to the drought tolerance in rooftops and can be used for urban greening.