[Objective] The purpose of this study was to explore the role of 1-deoxy-D-xylo-5-phosphate reductoisomerase (DXR) gene in the synthesis of monoterpenes in lilac (Syringa oblata), and to provide effective genetic resources and theoretical basis for floral fragrance molecular breeding of lilac. [Methods] Firstly, the SoDXR gene was cloned. Then, bioinformatics and subcellular localization were analysis, and qRT-PCR was used to analyze the gene expression patterns in different floral development stages and tissues. Finally, transient overexpression of SoDXR in the petals of snapdragon (Antirrhinum majus) was detected. [Results] The open reading frame (ORF) of SoDXR was 1425bp encoding 474 amino acids. SoDXR protein contains conserved domain of DXP_reductoisom, and has a similarity of up to 95% with Osmanthus fragrans and Olea europaea. Subcellular localization indicated that the protein was mainly located in the plastids, consistent with the software prediction results. Accompanied by flowering, the expression levels of SoDXR increased and then decreased, with the highest expression level in the initial openning stage. The SoDXR was differentially expressed in various tissues with the highest expression in petal and lowest in stem. Transient overexpression revealed that the expression level of SoDXR gene was significantly higher than that of control. Moreover, the main floral volatile components in snapdragon petals, myrcene and ocimene, were significantly increased by 15.03 and 4.83 times, respectively. [Conclusion] The SoDXR gene positively regulates the synthesis of monoterpenes in lilac, and SoDXR gene may play an important role in the synthesis of floral fragrance secondary metabolites.