Four plant species in Con Dao shared together a Vietnamese name as “cay Nua”. They have habits, tubers and leaves quite similar each other. However, they belong to 2 families, which have caused a lot of confusions in exploitation, cultivation and use in the life. Among of them, 2 species belong to the genus Tacca (Taccaceae) as T. leontopetaloides and T. palmate, 2 remained species belong to the genus Amorphophallus as A. macrophyllus and A. coudercii. The species T. leontopetaloides is cultivated for tubers making starch and T. palmate is collected in the wild for medicine. While the tubers of A. macrophyllus and A. coudercii are not as edible tubers. For avoiding confusion in exploitation and using, the article described 4 above species and supported new morphological characters and new distribution of 2 Amorphophallus in Con Dao island.