Abstract: Ten healthy chickens were selected for the observation of chicken thymus by microcirculation microscope in vivo. Transparent vascular specimens and tissue sections were prepared to observe the overall trend of micro vascular and the fine structure of vascular. The results showed that the blood serving thymus was mainly from vagus artery starting from the small dried branch of common carotid artery and extending to the visceral of the neck and the being skin in middle of neck, then branching into the thymus along the way. The branch divergenced into the vascular tree in the central portion close to the glands, forming capillary network after essence. These capillaries went vertically toward the thymus surface, or they would join the superficial capillaries plexus, or with the capillary bundle a distance to return medulla, they formed the capillary loops. Metarterole was connecting extensive venous plexus composed of irregular meshes, whereas the post capillary venule joined the venues at the cortico-medullary boundary and finally into blood vessels at the surface of the glands, thus forming the thymus vein, which emptied into the external jugular vein.