Objective: To study the effects of botulinum toxin -A (BTX -A) on the ultrastructural change of gastrocnemius muscle and relative tissue of spastic paralytic rats. Method: A total of 150 rats were randomly divided into four (A,B,C,D) groups. All rats of 4 groups were drilled a holl on the skull; rats of B,C,D groups were underwent electrical destroy at left pyramidal tract; after that saline and BTX-A were injected into gastrocnemius muscle of spastic paralytic group B rats and group C and D rats respectively; then let the group D rats to exercise in rolling cage. The ultrastructural changes of gastrocnemius muscle and related tissue of spastic paralytic rats in different period were studied by transmission electronic microscopy. Result: The ultrastructural changes of muscle and related tissues were more obviously in group C and D than that in group B. After 3 months the behaviors and ultrastructures of muscles and related tissues were improved in group D. Nerve sproutings were also observed in group C and D under transmission electronic microscopy. The pathologic changes were different at both sides of muscle membranes. Conclusion: The changes of ultrastructure in muscles after injection of BTX-A are more distinct than that in rats of single spasmodic models. The membranes of muscle cells can seemly prevent the penetrating of BTX-A. BTX-A maybe induces the nerve sprouting. Exercises can obviously improve the function of nerve and movement, and can promote the resume of muscular ultrastructure.