Deep vein thrombosis of the lower extremities is a common disease. This disease can be followed by lower limb edema, secondary varicose veins, dermatitis, hyperpigmentation, and depressed ulcers, which seriously damage the health of working people. The pathophysiological changes caused by venous thrombosis are mainly the various effects of venous return disorders that occur. The degree of venous blood return obstruction depends on the size and location of the involved vessels, as well as the extent and nature of thrombosis. After the formation of venous thrombosis, a series of pathophysiological changes caused by the increase of venous pressure on the distal side of the thrombus, such as the small veins and even capillary veins are in an obvious depressed state, the osmotic pressure of capillaries increases due to the change of venous pressure, and the permeability increases due to the lack of oxygen in the endothelial cells of blood vessels, so that the intravascular fluid components leak outward and move to the tissue interstices, often causing swelling of the limbs. If there is leakage of red blood cells outside the blood vessels, their metabolites contain iron-containing heme, forming skin pigmentation.