Stearoylacyl carrier protein Δ₉ desaturase(SAD) is a key enzyme that determines the content of plant saturated fatty acids and unsaturated fatty acids. This study obtained the ElSAD2 gene sequence based on the transcriptome database and analyzed its sequence and expression characteristics, then we identified the function of the ElSAD2 gene. The results showed that: (1) the cDNA length of ElSAD2 was 1 665 bp and ORF was 1 194 bp, encoding 397 amino acid residues. Phylogenetic analysis showed that ElSAD2 protein was closely related to RcSAD1 protein in Ricinus communis. (2) ElSAD2 was expressed in all tissues, with the highest expression level in seeds of 30 days after anthesis. (3) Genetic transformation showed that overexpression of ElSAD2 could increase unsaturated fatty acid content in defective yeast BY4389. (4) The instantaneous expression of ElSAD2 in tobacco leaves increased the contents of total fatty acid and oleic acid by 2.46% and 2.1%, respectively. It was found that ElSAD2 could efficiently catalyze the biosynthesis of monounsaturated oleic acid, which could be further applied to the improvement of oil yield and quality.