Abstract: Geomorphologic units of Hainan Island can be divided into four classes: geomorphic regions,sub-geomorphic regions,landform-genetic types,and micro relief.They are divided into two big geomorphic regions,called a north mesa plain and a south mountains region.They contain 14 sub-regions.There are mountains,hills,platforms,terraces,and plains.However,the dominant geomorphologic landforms are mesa and mountain that covers 32.6% of the whole area of Hainan Island.Taking into consideration of the kinds and directions of exogenic forces and history of geomorphic development,five geomorphologic genetic types,including erosional and denudation structural landform,denudational and erosional landform,riverine accumulation landform,marine-built landform,and volcano landform,are delimited