Abstract: The CRISPR-Cas13 system, an RNA-guided editing tool, has emerged as a highly efficient and stable RNA editing technique. Although the CRISPR-Cas13 system has been developed in several insect species, its application in lepidopterans has not yet been reported. In the present study, we evaluated the RNA cleavage activity of the CRISPR-Cas13 system in the silkworm (Bombyx mori), a model lepidopteran insect, both ex vivo and in vivo. We established two stable silkworm BmE cell lines expressing PspCas13b and CasRx, respectively. Further analysis demonstrated that both PspCas13b and CasRx effectively down-regulated the transcription of exogenously-introduced target and endogenous genes in these cell lines. In addition, we generated two transgenic silkworm strains, one expressing CasRx and the other expressing RNA-guided CRISPR RNA targeting Sex combs reduced (Scr). Further crossing experiments showed that CasRx induced a down-regulation of Scr transcription in silkworms, which impaired systemic growth of larvae. Overall, this study demonstrated that the CRISPR-Cas13 RNA editing system works efficiently in the silkworm, providing a potential alternative approach for RNA manipulation in lepidopteran insects.