Illumina HiSeq 4000 technology platform was used to construct the transcriptome database of Citrus aurantium L. at different developmental stages,and the key enzyme genes for the biosynthesis of alkaloids and flavonoids were mined to further study the biosynthesis of the medicinal components at the molecular level.A total of 133 155 Unigeness with an average length of 1 892 bp were obtained by Trinity assembly.According to KEGG metabolic pathway analysis,2 640 Unigeness were found to be involved in 13 metabolic pathways related to the biosynthesis of secondary metabolites.The genes involved in the biosynthesis of alkaloids and flavonoids were further analyzed,and nine key enzyme genes involved in the biosynthesis of alkaloids and flavonoids were screened.In this study,the dynamic transcriptional changes of active components biosynthesis were studied from two components for the first time,which enriched the genetic information and provided scientific basis for further analysis of the regulatory mechanism of biosynthesis of medicinal components of C. aurantium.