The effect of Sunphenon and Polyphenon 60 in oxidative stress response, myogenic regulatory factors, inflammatory cytokines, apoptotic and proteolytic pathways on H2O2-induced myotube atrophy was addressed. Cellular responses of H2O2-induced C2C12cells were examined, including mRNA expression of myogenic regulatory factors, such as MyoD and myogenin, inflammatory pathways, such as TNF-𝛼 and NF-kB, as well as proteolytic enzymes, such as 𝜇-calpain and m-calpain. The pre-treatment of Sunphenon (50 𝜇g/mL)/Polyphenon 60 (50 𝜇g/mL) on H2O2-treated C2C12 cells significantly down-regulated the mRNA expression of myogenin and MyoD when compared to those treated with H2O2-induced alone. Additionally, the mRNA expression of 𝜇-calpain and m-calpain were significantly (𝑝 < 0.05) increased in H2O2-treated C2C12 cells, whereas pre-treatment with Sunphenon/Polyphenon significantly down-regulated the above genes, namely 𝜇-calpain and m-calpain. Furthermore, the mRNA expression of TNF-𝛼 and NF-kB were significantly increased in H2O2-treated C2C12 cells, while pre-treatment with Sunphenon (50 𝜇g/mL)/Polyphenon 60 (50 𝜇g/mL) significantly (𝑝 < 0.05) down-regulated it when compared to the untreated control group. Subsequent analysis of DNA degeneration and caspase activation revealed that Sunphenon (50 𝜇g/mL)/Polyphenon 60 (50 𝜇g/mL) inhibited activation of caspase-3 and showed an inhibitory effect on DNA degradation. From this result, we know that, in stress conditions, 𝜇-calpain may be involved in the muscle atrophy through the suppression of myogenin and MyoD. Moreover, Sunphenon may regulate the skeletal muscle genes/promote skeletal muscle recovery by the up-regulation of myogenin and MyoD and suppression of 𝜇-calpain and inflammatory pathways and may regulate the apoptosis pathways. Our findings suggest that dietary supplementation of Sunphenon might reduce inflammatory events in muscle-associated diseases, such as myotube atrophy.