Abstract: Coral reef is a special engineering construction site, which is influenced by geological origin, biological effects, marine hydrodynamic and geological environment, etc. The research on engineering geological division is not only important in understanding and evaluating the engineering properties of coral reef deposits, but also has important guidance on coral reef engineering design and construction. Based on field geological survey, in-situ tests, drilling and a large number of laboratory experiments, analyses are conducted for geological origin of coral reef stratum, landform, stratigraphic configuration, mineral and chemical composition, and physico-mechanical properties of coral reef sediments. It is concluded that coral reef in the coast of Sanya can be divided into lagoon depositional area, sandbar area and underwater live corals accumulation area. Finally, evaluation is carried out for the engineering characteristics of each division, and suitability of construction is analyzed. The results have important guidance for geological survey of coral reef and engineering planning & design.

Key words: coral reef, engineering geological condition, engineering geological division