The sinus node of yak has been studied by the histological methods and transmission electron microscopy. The sinus node artery of yak was also determined by the injection-corrosion casting technique, the angiography, and histological methods. The results showed that the sinus node of yak contained an extensive framework of collagen and two main type cells: pacemaker cells (P cells) and transitional cells (T cells). The P cells had a perinuclear clear zone, contained less myofibrils, and appeared smaller mitochondria than T cells. The T cells were longer and slender than P cells, and had a variety of shapes. At the periphery of sinus node there were many nerve fibers and ganglions. Gap junction did not reveal reaction with anti-connexin43, but it was detected by electron microscopy in the central part of sinus node of yak. The sinus node artery of yak originated from left coronary artery more frequently (98%) than by right (2%). The artery located at the periphery of sinus node. It had an internal elastic membrane throughout its course, and a large nerve bundle was found running in a longitudinal direction.