Objective To explore the rule of changes in the myoblast stem cells (satellite cells) in the denervated and innervated muscles and to find out thecellular mechanism of the changes in the muscle morphology and function. Methods The denervated muscleatrophy models were established from 27 Wistar rats aged 1 month. One to six months after operation, examinations of the histology, histochemistry, and morphology were performed on the specimens from the bilateral triceps muscle of the calves of 3 rats in each month. Meanwhile, examination of the cell biology was performed on the specimens from the bilateral triceps muscleof the calves of 1 rat 1, 2 and 3 weeks after operation, and monthly for 1-6 months after operation. The innervation models were established from 35 Wistar rats aged 1 month. Immediately after the denervation, and monthly for 1-6 months after operation, 5 denervated rats underwent the nerve implantation. The changes in the electrophysiological index were observed dynamically until 8 weeks after the nerve implantation.Results After the denervation, the muscle wet weight and the muscle cell area decreased rapidly, but the content of the collagen fibers increased gradually. The number of the nucleus in the period of proliferationwas the greatest 3-4 months after the denervation, and then decreased rapidly.The muscle satellite cells began to increase obviously 3 weeks after the denervation, but 2 months later they decreased rapidly and 4 months later the number of the cells was the smallest. Four to five weeks after innervation, the muscle action potential could be induced, and the best innervation effect could be achieved in the implanted nerve after the 2-3 months on denervation, and at this time the differentiation ability of the satellite cells was the best. Conclusion Four months after the denervation of the skeletal muscle, an extremely small number of the satellite cells can make the muscle enter the irreversible atrophy. However, when the innervation is performed 2-3 months after the denervation, the actively-growing satellite cells can promote a better functional recovery ofthe atrophic muscle.