Coral reef, mangrove, and seagrass bed are important ecosystems in coastal areas and small islands which plays critical roles in maintenance of shorelines and lands on small islands. Those ecosystems have mutual relationships in providing effective protection of lands and lives on small islands. The objectives of the research are to calculate, to valuate, and to determine ecological adaptive capacity small islands of Guraici Islands. Field work was carried out at all 17 islands of Guraici Islands, where data collection and calculations of each ecosystem adaptive capacity of coral reef, mangrove and seagrass bed were made. Values of adaptive capacity for each ecosystem are found to range between 0.0 and 1.0 whereas values of the ecological adaptive capacity of every single island in Guraici Islands range between 0.0 and 3.0. The results of this research indicate that all small island ecosystems studied in Guraici Islands can be grouped into three categories of adaptive capacity, they are “medium, low, and very low”. Values of coral reefs adaptive capacity range between 0.0 and 0.58. Values of mangroves adaptive capacity range between 0.0 and 0.51. Values of seagrass beds adaptive capacity range between 0.0 and 0.51. Data analysis made also shows that small island ecological adaptive capacity in Guraici Islands has also belonged to three categories “medium, low, and very low”, where all their adaptive capacity values range between 0.37 and 1.64. Ten islands are in “Medium” category, six islands in “low” category, and one island is in “very low” category.