Dry stool first and then thin stool may be caused by intestinal dysfunction, intestinal tumor and other reasons. 1. Intestinal dysfunction: due to irregular bowel movement, the feces remain in the intestinal tract for too long, resulting in water being absorbed by the mucous membrane of the rectum, and after discharging the feces, the feces discharged first is drier, and the feces after that has more water content, so there will be the phenomenon of dryness followed by thinning. 2. Intestinal tumors: Due to the occupying lesions of intestinal tumors, it changes the stool properties, which leads to the symptoms of increased frequency of stools, thinning of stools, or dry stools at first and then scanty stools, and so on. It is recommended to develop the habit of having bowel movement on time and ensure a certain amount of water intake. If there are changes in bowel habits, such as dry stools followed by loose stools, accompanied by other symptoms, you should go to the hospital in a timely manner, under the guidance of a professional physician to determine the cause of the disease.