Abstract: High temperature is one of the major factors that threats to cucumber production. Cucumber grafted seedlings could alleviate the damage induced by high temperature stress, but the awareness of rootstock-used pumpkin varieties is insufficient. In a search for thermotolerace and morphological indexes, we collected 48 specimen rootstock-used pumpkins from different regions. Those varieties were treated with high temperatures (38℃ and 42℃) at germination and seedling stages, respectively, and screened for thermotolerance using UPGMA cluster analysis. Ten indexes (i.e., germination rate, germination potential, germination index, vigor index at germination stage, and plant height, stem diameter, fresh weight, dry weight, seedling index and hot injury index at seedling stage) were evaluated. These results show that the thermotolerance of 48 rootstock-used pumpkin varieties could be divided into 4 types at germination stage and seedling stage. In both development stages there were 2 moderately heat susceptible cultivars (samples 26, 27) and 11 heat sensitive cultivars (samples 6, 9, 10, 11, 13, 14, 17, 20, 36, 47, 48). The relative value of germination potential, germination index, vigor index, dry weight were credible indexes for identification.