Linoleic acid is synthesized by fatty acid desaturase 2(FAD2), which play an important role for produce polyunsaturated fatty acid in plant. The key enzyme for the conversion of oleic acid into linoleic acid was isolated from sunflower (Helianthus annuus L.), and designated as HaFAD22.The open reading frame (ORF) of HaFAD22 was 1 152 bp in length, which encoded 383 amino acids, with the isoelectric point of 8.56 and molecular mass of 43.96 kD. The genome intron survey showed that there is no introns in open reading frame region. Phylogenetic analysis showed that HaFAD22 protein shares high homologies with calendula (Calendula officinalis) and dove (Vernonia galamensis). qRTPCR analysis indicated that HaFAD22 was expressed in roots, stems, leaves, cotyledon, flowers and developing seeds, and the highest in leaves, the lowest in developing seeds. Furthermore, HaFAD22 in roots could be induced significantly by low temperature (5 ℃, 15 ℃), but repressed in leaves by low temperature (5 ℃, 15 ℃) and NaCl stress (300 mmol/L). Results in this experiment provide reference for further functional study on HaFAD22.