Abstract: Polyacetylenes (PAs) are a class of bioactive plant-specific defense compounds primarily produced by campanulid plants. Early PA biosynthesis is catalyzed by fatty acid desaturase 2 (FAD2). In this study, we identified the FAD2 gene family in Aralia elata (Miq.) Seem. and A. fargesii Franch., members of the Araliaceae family, a major source of PA, and analyzed their conserved motifs, domains, chromosome distribution, gene collinearity, evolutionary relationships, molecular evolution rates, and expression patterns. Results indicated that the FAD2 gene family in Aralia has undergone extensive expansion, likely through whole-genome duplication (WGD) or segmental duplication. The conserved motifs of FAD2, despite their different functions, were consistent, but diverged in representative Aralia species with different life forms (herbaceous vs. woody). Furthermore, A. elata possessed four different functional FAD2 genes, expressed differently in different tissues. This study holds important theoretical significance for the identification of Aralia species, the discovery of new genes for PA synthesis, and the elucidation of the molecular mechanisms underlying the high diversity of PAs in campanulids.