Pain in the lower abdomen when sitting down may be caused by a mass or tumor inside the abdominal cavity of the patient. When the patient sits or stands, the local pain is obvious or the pain increases because the small abdomen is squeezed, which may be caused by colon tumor, appendix tumor, appendix tumor, or even ovarian cyst or ovarian tumor. It is suggested that the patient should do abdominal CT examination, abdominal ultrasound examination to make preliminary judgment. If it is considered to be caused by intestinal tumor, further abdominal enhancement CT, colonoscopy and other related examinations are needed to further clarify. In addition, it may be caused by inflammatory lesions inside the patient’s abdominal cavity, such as chronic appendicitis and pelvic inflammatory disease, and if necessary, anti-infection and surgery are needed for treatment.