The invention belongs to the field of biomedical specialty and particularly relates to application of miR-125a-3p to preparation of a diagnosis kit of cardiovascular diseases. The diagnosis kit is capable of taking miR-125a-3p protein as a marker, detecting expression quantity of the miR-125a-3p protein in plasma, and carrying out early diagnosis of the cardiovascular diseases; meanwhile, the diagnosis kit has an obvious effect of regulating the functions of mononuclear macrophages, is capable of effectively and rapidly accelerating the phagocytosis of lipid components in blood vessels of themononuclear macrophages so as to control the inflammation levels of hyperlipidemia and arteriosclerosis, and has extremely excellent good application prospects.