[Objectives]  To further understand the molecular mechanisms underlying the overexpression of the Ras1^CA oncogene in the posterior silk gland (PSG) of Bombyx mori and how this improves silk yield at the transcriptional level. Transcriptomic data from differentially expressed genes (DEGs) in the cell cycle pathway of Ras1^CA-overexpressed and wild type PSG were analyzed and verified by quantitative real-time PCR (qRT-PCR). [Methods]  Deep RNA sequencing of silkworm PSG was carried out and KEGG pathway enrichment analysis was conducted on the DEGs. The DEGs in the cell cycle pathway was selected to be verified by qRT-PCR. [Results]  RNA-Seq revealed 2 636 DEGs in Ras1^CA-overexpressed PSG compared to wild type PSG. There were 42 DEGs distributed in the “cell cycle” pathway, including cyclin dependent kinases (CDKs), cyclins and transcription factors. Consistent with the transcriptomic data, qRT-PCR verification of the selected genes; cdk1, cyclinD1, cyclinD2, cdc7, cdh1, dp-1,2, indicated that all of these were significantly upregulated by Ras1^CA. [Conclusion]  Transcriptomic analysis revealed that there are a number of DEGs in Ras1^CA-overexpressed and wild type PSG. Ras1^CA-overexpression upregulates some DEGs in the cell cycle pathway that benefit silk gland growth and fibroin synthesis. These results advance our knowledge of the molecular mechanism underlying how Ras1^CA-overexpression in the PSG improves fibroin production and silk production.