This study investigates the molecular mechanism by which yaks (Bos grunniens) adapt to hypoxia based on lactate dehydrogenase (LDH). Three LDH1 variants of the yak were revealed in tissue extracts by electrophoresis, including LDH1-F, LDH1-M, and LDH1-S. Kinetic analysis using purified LDH1 variants showed that the yak LDH1-M variant exhibited a similar K (m) (NADH) and the same mobility on a gel as bovine LDH1, and the LDH1-F variant showed significant differences in K (m) values for NADH or pyruvate from the other two variants of yak LDH1 and bovine LDH1. Among the three muscles assayed, yak longissimus dorsi showed the highest LDH activity and the lowest malate dehydrogenase (MDH) activity; heart muscle was exactly the opposite. Our results suggest that the three LDH1 variants might play an important role in the adaptation to hypoxia.