Abstract: The synthesis of plant terpenoids is mainly through the MVA and MEP pathways. These terpenoids play an important role in plant growth and development, and also contain a large amount of terpenoids in plant floral volatiles. 3-hydroxy-3-methylglutaryl coenzyme A synthetase gene（HMGS） is a key enzyme gene in the MVA pathway, which mainly catalyzes the condensation of acetyl-CoA and acetoacetyl-CoA into 3-hydroxy-3-methyl Lipoglutaryl Coenzyme A（HMG-CoA） is a precursor rate-limiting enzyme for the synthesis of terpenes. In this study, Am HMGS was cloned from Antirrhinum majus ’Maryland’. The gene was 1 383 bp in length and encoded 460 amino acids. The expression of AmHMGS gene in flowers was expressed by spatio-temporal and tissue-specific RT-qPCR expression analysis. The expression level of AmHMGS gene in flowers was significantly higher than that in roots and leaves; the expression level was the highest in the initial stage; in the different flower organs of the flowering stage, the AmHMGS gene had the highest expression in the stamen and upper lobes, and the expression level in other flower organs was significantly different. The jasmonic acid inhibitors treated with different concentrations of fenidone were used to treat the petals of Snapdragon, and the expression of HMGS gene by RT-qPCR showed that fenidone could inhibit the expression of genes. The results of this study were to clarify the expression pattern of Am HMGS gene in Snapdragon, and lay a foundation for further study of the function of this gene and its signalling role in the floral release of snapdragon.