If stomach pain and lumbago occur after intercourse, the vast majority of them are due to chronic inflammation of the pelvis. As the pelvis itself has chronic inflammation, it will cause adhesions and large amount of exudation in the pelvic tissue, and after intercourse, the pelvis will be congested with blood, so it will lead to pain in the lower abdomen as well as lumbago. In addition, if the pelvic adhesions are caused by endometriosis, it will also lead to stomach pain and back pain after intercourse. Because endometriosis causes pelvic adhesions, the elasticity in the pelvic cavity decreases, so, under the action of external force, it can cause stomach pain and lumbar pain. In this case, gynecological examination is recommended to find out whether the uterine activity is normal and whether there is thickening in the bilateral adnexal area and tenderness in the sacral ligament, and ultrasound examination is recommended to find out whether there are foci of endometriosis in the pelvic cavity and then give treatment according to the cause.