The yellowish-black color of the stool is caused by the above factors such as gastrointestinal bleeding, gastrointestinal disorders and diet, and needs to be diagnosed by routine stool examination. First of all, when the human body has upper gastrointestinal bleeding, the blood will pass through the human digestive system and then excreted. During the digestion process, some iron in the blood is oxidized by the human body, thus causing the color of the stool to appear black, and some people will appear yellow and black because the blood and food are mixed together. Secondly, the peristaltic speed of the intestinal tract will be affected when the intestinal tract is disordered, and the stool in the intestinal tract will be excreted more slowly because it stays in the intestinal system for a relatively long time and forms persistent stool, which is black in color and will appear black and yellow when combined with new stool. Finally some people are caused by eating black colored foods in their diet, and because these pigments cannot be absorbed by the body, they appear black and yellow when mixed with the stool formed from normal foods.