Under normal circumstances, the tongue of a 3-year-old child should be relatively red and moist. If the tongue is thick and white suggesting the existence of digestive system problems, pay attention to the following aspects: 1. Maybe the child’s oral hygiene is not done well, not to develop the habit of brushing teeth in the morning and evening and rinsing the mouth after meals. 2. Pay attention to the possible existence of upper digestive system diseases, such as the existence of reflux gastroesophagitis, gastritis, gastric ulcer, duodenitis, duodenal ulcer and so on. There may be diseases of Helicobacter pylori infection.3. The child’s poor digestive and absorption functions and weak spleen and stomach functions lead to increased accumulation of gas in the child’s digestive system, causing thick white tongue coating.4. Pay attention to the presence of intestinal parasites in the child, such as roundworms, pinworms and other food indigestion.