Abstract: Fatty acid desaturases catalyze the insertion of a double bond at the delta position of fatty acids. At least 5 fatty acid desaturases exist in plants: FAD2, FAD3, FAD6, FAD7 and FAD8. They are categorized into two classes according to the doublebond position introduced (i.e., w-3 including FAD3, FAD7 and FAD8, and w-6 including FAD2 and FAD6). Most plant cells contain more than one copy of each gene — FAD2, FAD3, FAD6, FAD7, FAD8 — for fatty acid desaturase. The copy number of a desaturase gene varies among plant species. Even for the same gene in the same plant, different copies may vary in sequence, expression regulation and function. We provide an overview of the research advances into fatty acid desaturases in terms of their classification,copy number, gene structure, gene function, gene regulation and applications in plants.