Objective To explore the effect of corn oligopeptide (COP) on dexamethasone-induced muscle atrophy. Methods Forty-nine male Sprague-Dawley rats aged 8 weeks were divided into blank group (n=10) and model group (n=39). The rats in the model group were intraperitoneally injected with dexamethasone (1.0 mg/kg), and the rats in the blank group were injected with normal saline. After 19 days, one rat in the blank group and three rats in the model group were taken to observe whether the model was successfully constructed. After successful modeling, the rats in the model group were randomly divided into model control group, COP low-dose group (COP-L group, 0.5 g/kg), COP medium-dose group (COP-M group, 1.0 g/kg) and COP high-dose group (COP-H group, 2.0 g/kg), with 9 rats in each group. After 33 days, the grip strength of the rats was measured, and then the gastrocnemius, soleus, tibialis anterior and metatarsal muscles were separated and weighed, and muscle fiber diameter, relative expression of Atrogin-1 and MuRF-1 mRNA were measured. Non-targeted metabolomics of gastrocnemius muscle were measured. Results Compared with that in the blank group, the body weight of rats in the model group reduced (P<0.05), and myofibril rupture was observed, indicating that the model was successful. Compared with those in the model control group, the grip strength increased in the COP-L and COP-M groups (P<0.05); the muscle coefficients of gastrocnemius and soleus in the COP-L and COP-H groups increased (P<0.05), and the muscle coefficients of plantaris in the COP-L and COP-M groups increased (P<0.05); the muscle fiber diameter of the tibial anterior muscle increased in the three doses of COP groups (P<0.05), and the muscle fiber diameter of the plantaris muscle increased in the COP-M and COP-H groups (P<0.05); the relative expression of Atrogin-1 mRNA decreased in the three doses of COP groups (P<0.05), while the relative expression of MurF-1 mRNA in the COP-L and COP-H groups decreased (P<0.05). The amino acid synthesis pathway, glycolysis pathway, and acid metabolism pathway were activated in gastrocnemius muscle. Conclusions COP can significantly improve the muscle atrophy induced by dexamethasone. The mechanism may be related to the decrease of Atrogin-1 and MuRF-1 expression in ubiquitin-proteasome pathway and the increase of amino acid biosynthesis.