The relationships between Araceae diversity and altitude gradients in mountain ecosystem at Doi Suthep-Pui National Park, Chiang Mai Province in Thailand, were studied during January 2016-March 2018. The strip-plots, 10 m × 1,000 m along the five nature trails, were established from 300-500, 501-800, 801-1,100, 1,101-1,400, 1,401-1,685 m above mean sea level (amsl). Twenty species of 11 genera were found. Alocasia navicularis and Lemna sp. were found at 300-500 m amsl, wild taro (Colocasia esculenta) was at 300-800 m amsl, A. acuminata was at 300-1,400 m amsl, while Amorphophallus krausei, Hapaline benthamiana, Lasia spinosa, Rhaphidophora chevalieri and R. megaphylla were at 501-800 m amsl, but dwarf taro (C. affinis) was at 501-1,400 m amsl, Homalomena aromatica was at 801-1,100 m amsl, A. fuscus, A. thaiensis were at 801-1,685 m amsl, A. yunnanensis was at 1,101-1,685 m amsl, only five species, Arisaema consanguineum, A. kerrii, Remusatia hookeriana, R. peepla and Sauromatum horsfieldii were found at 1,401-1,685 m amsl. Species diversity in the rainy season was the highest (1.75), the top five dominant species were dwarf taro (C. affinis), wild taro (C. esculenta), A. fuscus, A. acuminata and A. thaiensis (importance value index (IVI%): 61. 54, 24.13, 17.12, 16.52 and 9.60, respectively). In dry season, the dominant species was wild taro. The altitude gradients showed the main effect on diversity and distribution of Araceae.
