Lower extremity vein thrombosis is a common venous blockage disease of the lower extremities, which is caused by the blockage of blood clots in the venous vessels, resulting in a series of symptoms of venous stasis. The main points of observation of lower extremity vein thrombosis include the following aspects, first, to observe the patient’s symptoms, pay attention to the general lower extremity vein thrombosis patients will suddenly swelling and pain. Severe patients will have increased skin temperature and flushing. Patients with such changes should suspect the formation of venous thrombosis of the lower limbs. Second, the patient’s general vital signs should be observed. If lower extremity venous thrombosis is formed, the thrombus is unstable in the acute stage causing dislodgment due to the patient’s inattention and possibly lack of regular treatment. Patients will show serious clinical symptoms such as dyspnea, profuse sweating and syncope, which is a manifestation of pulmonary embolism. At this time, it is necessary to pay attention to the changes of vital signs such as blood oxygen saturation, blood pressure and heart rate of patients to avoid adverse consequences such as serious sudden death. Thirdly, the changes of leg diameter should be observed during the treatment. Generally, the effect of venous thrombosis will be more obvious after regular anticoagulation treatment. It is recommended to observe the changes of skin temperature, skin color and even swelling of the patient every day, which is used to assess the condition.