Insulin-like growth factorⅠ(IGF-Ⅰ) and insulin are two important members in the insulin family with highly homologous structure. They bind to the homologous receptor and produce similar physiological function, but the major function is different. The major function of IGF-Ⅰ is growth-promoting whereas insulin plays a key role in the glucose uptake and metabolism. The bases of the physiological function and its expression of a protein are the molecular structure of the protein and the molecules involved in the expression of the function, such as receptors and signal molecules, etc. The recent progresses in the studies on the structural basis and molecular basis of physiological function of IGF-Ⅰ and insulin are reviewed.