In this study, we analyzed the genetic diversity and population structure of 90 A. oxyphylla accessions from Hainan island using amplified fragment length polymorphism (AFLP) markers. These 90 accessions were composed of 15 populations from different geographic locations and divided into 4 clusters (A, B, C, and D) using the Unweighted pair group method based on arithmetic average (UPGMA). The genetic similarity between individuals ranged from 0.47 to 1.00 (average of 0.74), and most accessions from the same geographic population were grouped together. Principal coordinate analysis (PCA) showed a clear distinction among three clusters (A, B and C). Based on the loci information, the population structure analysis results by STRUCTURE and TESS were consistent with the clustering of PCA. Nine AFLP primer combinations generated 1537 polymorphic bands displaying rich polymorphism, thus indicating high genetic diversity among these 15 populations with an average Nei’s gene diversity of 0.1328 ± 0.160. In conclusion, AFLP markers efficiently analyzed the genetic diversity in A. oxyphylla, demonstrating highly significant genetic variation within and among populations. However, intrapopulation genetic variance was much higher than interpopulation variability, suggesting that efforts should be made for in situ germplasm conservation and resistant varieties cultivation.