Lactate dehydrogenase (LDH, EC1.1.1.27) is a glycolytic enzyme composed of four subunits with molecular weight of 130-140KDa. It exists in the cytoplam of all tissues and cells in the body, and the content of kidney is higher. There are six forms of LDH isoenzyme, which can be separated by electrophoresis, and its distribution has obvious tissue specificity. LDH can catalyze the reversible transformation of pyruvate and lactate. It is an important enzyme involved in the anaerobic glycolysis and gluconeogenesis. The normal range of LDH in human serum is 135-215u / L. when endocrine disorders or overworked, LDH is easy to be low, which can be repaired after conditioning; the high level of LDH is due to pleural and ascites caused by pulmonary infarction, malignant anemia, shock and tumor metastasis, which is more serious.