Adults with dark green stools are considered to be caused by dietary factors, rotavirus infection and intestinal flora imbalance. 1. Dietary factors: such as eating a lot of green vegetables, such as spinach, Chrysanthemum, broccoli, etc., because green vegetables contain a lot of chlorophyll, not fully digested and absorbed chlorophyll will be discharged with the feces, so the feces is dark green and black. 2. Rotavirus infection: rotavirus is a double-linked RNA virus, which mainly manifests as fever, abdominal pain, vomiting, nausea, and yellowish-green watery diarrhea after infection, and can cause dehydration in severe cases. 3. Intestinal flora imbalance: it can cause indigestion and other symptoms, such as postprandial bloating, abdominal pain, early satiety, acid reflux, nausea, etc. Due to indigestion, the food can’t be fully digested and absorbed, which leads to dark greenish black feces. There are many other reasons for dark green and black stools, so it is advisable to seek medical advice to make a clear diagnosis and carry out targeted treatment.