| The cecum tonsils of healthy Chinese yellow quail with ages of 0, 1, 2, 3, 4, 5, 6, 10, 14, 18, 22, 26, 30, 34 and 38 weeks were collected for the microstructure and the ultrastructural observation. The results showed that the cecum tonsil of Chinese yellow quail was located at the base of the cecum at the ileocecal-rectal junction, and the basal part of the cecum tonsil near the cecum was easily separated from other parts due to the thick and wide of the cecum wall. The cecum tonsil existed during the incubation of quails, and had a complete external shape at 0-38 weeks of age with smooth and full surface. The structure of the cecum tonsil was divided into mucosa, submucosa, muscular layer and serosa from the inside to the outside and the mucosa included epithelium, lamina propria and intestinal glands. The endoplasmic reticulum, mitochondria, lysosomes and intestinal villi with clear structure were observed under transmission electron microscopy, and mitochondrial cristae was clearly visible. The absolute weight, length and width of cecum tonsils gradually increased with age, reaching the maximum at 6-week age, and kept unchanged at 10-38 weeks of age. It showed that the development of cecum tonsil of Chinese yellow quail gradually developed after their birth. The cecum tonsil developed rapid at 0-6 week of age, matured at 6-week age, and kept matured to 38-week age.