Infancy and early childhood are critical periods for the development and maturation of the intestinal flora. Mounting studies have demonstrated that changes in the intestinal flora during these periods may have profound effects on the growth and development, energy metabolism, maturation of the nervous and immune systems of infants and children. This article reviews the evolution of the composition and function of the intestinal flora in infants and young children during their development and maturation, as well as the factors influencing it. This article is expected to provide a reference for strategies to improve growth and development of infants and young children via regulation of the intestinal flora.