As a traditional spicy condiment, Zanthoxylum armatum var. novemfolius is of high economical and medicinal value. Despite the long history of human cultivation, the molecular mechanisms underlying flower development are still poorly understood in Z. armatum. In this study, we performed de novo transcriptome assembly and comparative analysis of female and male flowers in Z. armatum. A total of 94,771 unigenes were obtained, and 50,605 unigenes were successfully annotated against the public database. Transcriptome data showed that 20,431 annotated unigenes were differentially expressed genes. KEGG enrichment analysis revealed that the most representative pathway was plant hormone signal transduction. Among them,41,16,41,27, 95,and 40 unigenes were involved in the biosynthesis and signaling of abscisic acid, ethylene, cytokinin, gibberellin, auxin, and jasmonic acid, respectively. Transcription factors also played crucial roles in flower development, such as AGL11, PMADS2, and NAC. These results provided an important basis for characterizing the potential mechanism of flower development and enriching the knowledge of reproduction genetics in Z. armatum.