Objective：To study the ultrastructural morphological changes at millisecond time course level in skeletal muscle during excitation-contraction coupling after electrical stimulation. Methods: Two-way infrared detectors with a computer to control the signal of electric stimulation and quick freezing fixation were employed in this test. The ultrastructure of toad skeletal muscle was studied by transmission electronic microscopy after its skeletal muscle was stimulated in 0.8, 5.6, 8.4 ms. The skeletal muscular ultrastructure at known millisecond time course were observed following quick-freezing after a single electrical stimulation. Results:The space between sarcolemma and muscle myofibril was strikingly narrowed from 0.8 ms to 8.4 ms after electric stimulation, and 2 holes were observed in the front of sarcoplasmic reticulum membrane at the same time. Conclusion: During excitation-contraction coupling, the sarcolemma has positional shaft and space changes with myofibril when depolarization occurs, besides, there are small holes on the sarcolemma when skeletal muscles contract.