The invention discloses a preparing method of oyster active extract having functions of producing sperm to tonify the kidney and improving sexual function. The oyster active extract has the functions of producing the sperm to tonify the kidney and improving the sexual function. A composition mainly comprising the oyster active extract as a main active ingredient further comprises Epimedium herb, astragalus root, root of hairy asiabell, fruit of Chinese wolfberry, common Macrocarpium fruit, prepared rehmannia root, thinleaf milkwort root-bark, rhizome of oriental water plantain, licorice root and Indian bread. The preparing method includes special debitterizing, papain hydrolysis, fermentation-based deodorization via activated carbon and yeast, secondary debitterizing via beta-cyclodextrin embedding with mycose, decoloring via diatomite, color optimizing via bamboo leaf flavonoid and neutral sodium phytate, and taste optimizing via compound flavoring (comprising glucose, fructo-oligosaccharide and xylitol). The preparing method has the advantages that the process is advanced, the formula is scientific and reasonable, the nutrients are complete, the fishy smell is slight, the composition has natural flavor and the functions of producing the sperm to enhance the kidney, resisting fatigue, improving the sexual function and enhancing the body immunity, and the composition assists in treating symptoms, such as impotence, spermatorrhea and premature ejaculation, caused by deficiency of kidney-yang or deficiency of kidney-yin.