There are many causes of leg swelling, including deep vein thrombosis and filariasis, but deep vein thrombosis and filariasis usually occur more often in unilateral leg swelling, and rarely in both legs at the same time. There are many causes of edema, including low-protein edema, cardiogenic edema, and nephrogenic edema. Low-protein edema is mainly caused by patients’ malnutrition or not eating for a long time, as well as advanced tumor malignancy, etc. It is manifested by low albumin in blood plasma, and then the fluid in blood plasma enters the tissue interstitial space through the blood vessel wall, so it is manifested as leg swelling. Because the legs are the lowest after the body stands, edema starts from the ankles and calves, and then gradually becomes swollen in both legs at the same time. If it is a tumor, tumor eradication or chemotherapy may be required, and albumin input is needed to correct hypoproteinemia; if it is cardiogenic edema, it is usually caused by cardiac insufficiency, hypertension, etc., which leads to less cardiac blood return and blood pooling in the lower extremities, thus causing swelling in both legs at the same time.