Understanding interspecific relationships among dominant tree species in endangered plant communities enhances our knowledge of their ecological behaviors,especially regarding resource utilization and community succession phases,providing a theoretical foundation for conserving regionally endangered plants and restoring natural vegetation. This study analyzed the niche and interspecific associations of dominant tree species with field investigation data from communities of Heritiera parvifolia in Diaoluo Mountain of the Hainan Tropical Rainforest National Park. The analysis utilized the Shannon and Levins niche width index,Levins niche overlap index,variance ratio (VR),Chi-square test (χ² test),and Spearman's rank correlation coefficient test across the middle and small arbor layers and the large and middle shrub layers. The results showed that: (1) The importance values and niche width of Heritiera parvifolia were greater across various forest layers. This suggested that Heritiera parvifolia occupied a dominant position in the competition for community resources. The importance values of Vatica mangachapoi in the middle and small arbor layers,as well as in the large shrub layer was high,However,its niche width was significantly smaller than that of Heritiera parvifolia. The frequency of distribution had a greater effect on niche width. (2) The dominant tree species in the large shrub layer had the highest number of species pairs (188 groups) with niche overlap and the lowest number in the middle shrub layer (137 groups). This finding suggests that the dominant tree species in the middle shrub layer process a heightened capacity for environmental adaptation and resource utilization. Heritiera parvifolia had the highest number of species pairs (15 groups) with significant niche overlap in the small arbor layer,and interspecific competition was intense. (3) The dominant tree species in the middle arbor layer showed an overall insignificant positive association,but the dominant tree species in the small arbor layer,as well as large and middle shrub layers,demonstrated a significantly positive contributing to high community stability. (4) The χ² test and Spearman's rank correlation coefficient test further indicated that a predominance of positive linkages between species facilitated coexistence in the small arbor and middle shrub layers. However,the majority of species pairs in different forest layers were not significantly correlated,and the correlation among species was weak. Most species demonstrated high degrees of independence.