Abstract: Tongtianluo cave is located in the Karst region of Ruyuan county, in the north part of Guangdong province(24°59′N;l13°7′E). It is a huge vertical cave formed by the subsidence of the earth′s surface, with precipitous wall. The diameter of the cave is 73m at its mouth, and 140m at its bottom (along the widest direction). There is no record of exploration to the cave before ours. The evergreen broad-leaved forests were discovered on a areas of 3500m2 at the bottom of the cave, with lots of vines and Pteridophytes. The 12 species of Pteridophytes belonging to 8 genera and 6 families; and 80 species of Angiosperms belonging to 61 genera and 46 families were recorded. The existence and development of these plants indicated that human impact was little in the cave. The characters of the flora in Tongtianluo cave had much to do with the special ecological factors in it, i.e., the low illumination and calcareous clay soil.