Abstract: As a critical enzyme in the lipid biosynthetic pathway, fatty acid desaturase 2 (FAD2) is responsible for the desaturated conversion of oleic acid (18∶1) to linoleic acid (18∶2). With the combination of degenerate PCR and RACE methods, a full-length cDNA of FAD2 fragment was cloned from the developing Xanthoceras sorbifolia embryos that are rich in linoleic acid and oleic acid. Sequence analysis revealed that X. sorbifolia FAD2 has three N-glycosylation sites and several phosphorylation sites in addition to three conserved histidine motifs and an aromatic amino acid enriched signal YRNKL at the C-terminus. Agrobacterium-mediated X. sorbifolia FAD2 was expressed inArabidopsis thaliana fad2 mutant to identify its physiological function. The results of gas chromatograph (GC) analysis indicated that the introduction of X. sorbifolia FAD2 in Arabidopsis fad2 mutant resulted in the generation of linoleic acid, a fatty acid normally not existing in Arabidopsis fad2 mutant. This confirmed that the encoded enzyme by cloned X. sorbifolia FAD2 has the activity to catalyze the desaturated conversion of oleic acid (18∶1) to linoleic acid (18∶2).