When the “sperm test” is unsatisfactory or the “sperm test” is normal but fertilization fails repeatedly, the man will usually check the “seminal plasma biochemistry”, “HDS & DFI”, etc. to further find out the cause. HDS & DFI” in order to further find out the cause, this article mainly focuses on the common test items in “Seminal Plasma Biochemistry”. Seminal plasma is the internal environment for sperm development and maturation, and “Seminal Plasma Biochemistry” is a biochemical test of the components of seminal plasma. 1. Lactate dehydrogenase isoenzyme C4 (LDH-C4) is only found in mature testes and spermatocytes of all levels of human and mammals, and it is a sperm-specific isoenzyme, which can be used as an indicator to reflect the state of spermatogenesis of testes and to evaluate the quality of semen as well as the ability of fertilization. Neutral α-glucosidase is an enzyme secreted by the epididymis, which can catalyze the production of glucose to supply energy for sperm metabolism and movement. Neutral alpha-glucosidase is closely related to sperm maturation, motility and fertilization. In some pathological conditions, such as epididymitis and vas deferens obstruction, the enzyme in seminal plasma shows a decrease in content and vigor. Fructose, secreted by the seminal vesicle glands, is the main source of energy for spermatozoa, and the fructose content directly affects spermatozoa’s energy acquisition and fertilization process. It can be used to judge the secretion function of seminal vesicle glands. Since the secretion of fructose is affected by androgens in blood, fructose can also indirectly reflect the function of testicular interstitial cells in the distribution of androgens. In obstructive azoospermia patients seminal plasma fructose content is low, non-obstructive azoospermia patients seminal plasma fructose concentration is high. 5, seminal plasma zinc Zinc in seminal plasma is secreted by the prostate gland, which has the function of maintaining the stability of sperm cell structure, maintaining the stability of sperm chromatin, reducing the damage of oxygen radicals to sperm, as well as resisting infection, so as to maintain good sperm activity. Zinc content in seminal plasma can be used as one of the indicators of prostate function. 6, elastic scleroproteinase A proteinase secreted by leukocytes during inflammation of the reproductive tract, which can be used as a marker for hidden inflammation of the reproductive tract in men. “Seminal plasma biochemistry reacts to the functional status of different accessory glands of the male reproductive tract, and the analysis of different combinations of the results can help to analyze the etiology of azoospermia, oligozoospermia, hypospermia, teratozoospermia and semen liquefaction abnormalities, and it can be used to locate and diagnose the site of obstruction in obstructive azoospermia.