Abstract: In order to clarify the roles of myostatin in myofibril damage and investigate the measures to improve the production and quality of muscle mass in livestock or control the muscle atrophy in human, the serious stress models of mice were made with highdose dexamethasone, and the effect of physiologicaldose insulin on the dexamethasoneinduced myofibril damage and the relationship between the effect and myostatin expression were researched. In addition, the intervention effect of myostatin gene immunization on the dexamethasoneinduced myofibril damage was studied. The results showed that: dexamethasone upregulated the expression of myostatin gene and caused the serious damage of myofibril and swelling of mitochondria, while insulin attenuated the effects of dexamethasone; myostatin gene immunization reduced the myofibril and mitochondria damages induced by dexamethasone. The results suggest that myostatin is one of key factors for myofibril degradation and the role of myostatin may be attributed to the stimulation of mitochondrial function by myostatin.