Abstract: Regional geological, hydrogeological, and soil environment quality and geologic hazard and so on are the primary influential factors that affect the geological environment quality in northeastern Hainan island. Seven evaluating key elements and eleven evaluating factors,including the regional climate, geological setting, geologic hazard, soil environment quality, groundwater resource, human activity and vegetation condition, are selected to constitute an evaluating system and a mathematical model on the basis of the weighted average method is employed to valuate the regional geological environment quality in the northeastern Hainan. The evaluating result indicates that the geological environment quality in the northeastern Hainan is statistically good quality. 22.3% of the studied area, up to 4 075 square kilometers, belongs to the high class of quality, including the volcanic mesas, hills, and erosion deposits; and 69.3% of the studied area, up to 9 700 square kilometers, belongs to the good class of quality, continuously distributed at different geological reliefs; while the remaining 8.4% of the studied area, 1 225 square kilometers, belongs to the middle class quality, mainly distributed in serious geologic hazard area including soil water loss, land desertification etc.

Key words: geological environment, evaluation, weight value and weighted average method, Hainan island