Pressure sensation in the left abdomen when sitting may be due to abdominal tumor, abdominal fluid accumulation and so on. 1. Abdominal tumor: when there is a tumor in the abdominal cavity, the pressure in the abdomen will rise when sitting, and the pressure on the tissues near the tumor will be caused by the reason of body position, so there will be a feeling of pressure, and it is necessary to improve the examination to clarify the location of the tumor, perform surgical resection, and postoperative chemotherapy if necessary. 2. Abdominal fluid accumulation: for example, ascites occurs in cirrhosis, the amount of ascites will make the pressure in the abdominal cavity rise significantly, then there will be obvious pressure when sitting, then we can consider abdominal puncture drainage to reduce the symptoms. 3. Other: such as obesity. Appearance of the above symptoms must go to the hospital in a timely manner to clarify the diagnosis and timely treatment.