The deep veins are the main conduit for the return of blood to the heart and are located in the deep surface of the deep fascia, between the muscles, the deep veins mainly include the deep veins of the lower limbs, femoral veins, popliteal veins, anterior and posterior tibial veins, peroneal veins, iliac veins, inferior vena cava, superior vena cava, and jugular veins. The deep veins are the main vessels that return to the heart, and the superficial veins are located under the skin fascia, also known as subcutaneous veins, and the deep veins are mostly accompanied by arteries, and the superficial veins are not accompanied by arteries, and the veins eventually converge into the deep veins. The biggest risk of deep veins is the formation of thrombosis, which can lead to fatal pulmonary embolism, so attention should be paid to deep vein thrombosis.