Abstract:The caloric values (containing ash)of main plant species in a tropical mountain rain forest at Jianfengling, Hainan Island of China were measured by sampling 67 tree species, 10 shrubs and 6 lianas. The results indicated that the caloric values for tree species were generally higher, and the values of the leaf, stem, branch, bark, root and the plank-buttress were 20470.2, 19523.2, 19401.2 19325.0, 19250.4 and 19454.5J/g respectively according to average values of 67 tree species. Caloric values for shrubs were lower than trees’, the values for the leaf, shoot and root being only 18566.4, 18730.1 and 18530.4J/g respectively. Woody lianas had higher caloric values than herbal lianas. There were significant difference in caloric values among different species. Generally speaking, the megaphanerophyte plants had higher caloric values than nanophanerophyte plants. It is clear that the values were related to the plant life-form. Different individuals of the same species were not obviously different in caloric values. It was initially proved that some tropical plants contained certain amounts of elements such as Si, Fe, Mn, Mg, Cu, Ca, and Zn. indicating that tropical plants possessed a particular bio-geochemical cycling pattern. These elements could form oxides after plants being burned, therefore, this problem should be further studied in the future.