Taking the hickory(Carya cathayensis Sarg.)embryo as the test material, five periods (75, 85, 100, 109 and 127 days after pollination)of hickory embryo which are critical for the oil synthesis and integration are measured by gas chromatography to study the law of hickory oil. Additionally, Stearoyl- ACP desaturase genes(CcSAD-1, CcSAD-2, CcSAD-3)and fatty acid desaturase genes(CcFAD2, CcFAD3-1, ... [Show full abstract] CcFAD3-2, CcFAD3-3, CcFAD6, CcFAD7, CcFAD8-1, CcFAD8-2, CcFAD8-3)were studied by quantitative real-time PCR. The results revealed that hickory oil mainly composed of palmitic acid (C16:0), stearic acid(C18:0), oleic acid(C18:1), linoleic acid(C18:2)and linolenic acid(C18:3);hickory is a high oleic species. In addition, quantitative results showed that with the increase of Stearoyl- ACP desaturase genes expression, the oleic acid content in hickory oil increased and reached dynamic balance. Gene expression profiling and lipid analysis in hickory fruit during development identify CcSAD-3 as the main gene responsible for the oleic acid content in hickory oil. Meanwhile, with the increase of oleic acid content in the hickory oil, the expression of CcFADs increased, and the proportion of unsaturated fatty acids in hickory oil increased. © 2018 Editorial Office of Acta Horticulturae Sinica. All rights reserved.