Coral islands’ stressful environments (high temperature, drought, intense light, and salinity) have important impacts on plant survival and growth. Therefore, it is necessary to prioritize highly adaptable plant species for coral islands. To investigate this, we assessed the physiological responses and nutrient absorption of three woody plants – Casuarina equisetifolia, Morinda citrifolia, and Scaevola taccada – at the three sampling sites (CK, Guangzhou City; S1, coral island, Sansha City, added garden soil; S2, coral island, Sansha City, unadded garden soil) in China. The results showed that: (1) among the three plants, M. citrifolia showed the best physiological adaptation. (2) M. citrifolia adapts to coral island environments through elevated leaf-soluble protein content and reduced superoxide dismutase (SOD) activity to increase tolerance to osmotic stress. (3) Soil composition plays an important role in plant responses to harsh environments. This study provides basic data on the physiological responses and nutrient absorption of three plants grown on coral islands, an essential reference for revegetation and restoration of tropical coral islands.