Ras homologue enriched in the brain (Rheb) is an important positive regulator on the upstream of the mammalian mechanistic target of rapamycin (mTOR) signaling pathway. The cDNA sequence encoding Rheb in Eriocheir sinensis (EsRheb) was cloned using RT-PCR in order to investigate the role of this gene in the regulation of growth, development, and nutrient metabolism of Eriocheir sinensis via the mTOR signaling pathway. The sequence and structural characteristics of EsRheb were analyzed using bioinformatics. The tissue distribution of EsRheb mRNA and the effects of animal starvation and eyestalk ablation on EsRheb transcription were detected using qRT-PCR. The results showed that EsRheb cDNA encoded 182 amino acids; its amino acid sequence, conserved domain, and functional sites were highly similar to the Rheb of a wide range of species; and its three-dimensional structure was highly consistent with that of human Rheb. EsRheb mRNA expression was high in the hepatopancreas, stomach, myocardium, skeletal muscles, and Y organ, but was much lower in the eye stalk. Starvation treatment of animals significantly decreased the transcriptional expression of EsRheb in the skeletal muscle but had no significant effect on its expression in the hepatopancreas. The removal of the eye stalk significantly increased the transcriptional expression of EsRheb in the Y organs and skeletal muscles. This study provides a basis for elucidating the function of EsRheb in regulating the mTOR-mediated growth and metabolism of E. sinensis.