Promoting rumen development is closely related to the health and efficient growth of ruminants. In the present study, we aimed to assess the impact of YAP1/TAZ on RE proliferation. The transcriptomic expression was analyzed to investigate the potential regulatory networks. The results indicated that GA promoted RE cell proliferation, while VP disrupted RE cell proliferation. The Hippo, Wnt, and calcium signaling pathways were altered in cells following the regulation of YAP1/TAZ. Upon YAP1/TAZ activation through GA, the CCN1/2 increased to promote RE cell proliferation. While when the YAP1/TAZ was inhibited by VP, the BIRC3 decreased to suppress RE cell proliferation. Thus, YAP1/TAZ may be potential targets for regulating RE cell proliferation. These findings broaden our understanding of the role of YAP1/TAZ and their regulators in RE and offer a potential target for promoting rumen development. Overall design: GA-017 (GA) and verteporfin (VP) are identified as an efficient activator and inhibitor for YAP1/TAZ, respectively. GA can activate YAP1/TAZ by inhibiting their phosphorylation and promoting their nuclear translocation (Aihara et al., 2022). VP disrupts the YAP1/TAZ-TEA domain transcription factor (TEAD) mediated transcription and suppresses downstream gene expression (Brewer et al., 2021). Thus, the RE cells were treated with either GA (GA group) or VP (VP group), or left untreated (Con group), to assess gene expressions.