Objective To study the characteristic of histological structure of the pineal gland of the adult yak. Methods HE and AchucarroHortega staining, light microscopy and transmission electron microscopy were used. Results The pineal gland was composed of pinealocytes, occasional glial cells, capillaries and neural elements. The pinealocyte appppered clear electronic density and its cytoplast included numerous mitochondria, rough and smooth endoplasmic reticulum, microtubules, microfilament and ribosome.Golgi complex was rare. The typical heterogenous organelle of pinealocyte of yak was spherical synaptic ribbon, which located near the plasma membrane. The glial cells contained abundant of mitochondria, and their processes which appeared bulbous invested the pineal periphery and incompletely separated the pinealocytes. Synapse and junctional complex existed between the pinealocytes and glial cells. Capillaries in pineal gland of the yak were belong to continuous capillaries, and pigment cells were observed around the vascellum in the gastrdistally of the pineal gland. Conclusion Neuroepithelial and epithelioglandular cell conjuction can be observed in the pineal gland of adult yak. Capillaries are belong to continuous capillaries. There are aboundant of organelle except Golgi complex in the pinealocyte.