Children with delayed brain development will have the following symptoms: 1. poor sucking ability, the earliest symptom that babies with mental retardation show is difficulty in feeding, can’t suck, and easily spit up milk. 2. dull expression, still can’t show natural smile at 6 months. 3. backward motor development, mainly showing that the head can’t stand up at 4 months, the hand can’t actively grasp objects at 6 months, can’t sit steadily at 8 months, and can’t stand alone at 14 months. 4. 4.Outlook characteristics are obvious, such as wide eye spacing, slanting eyes, collapsed nose, tongue dragging outside the mouth, drooling. 5.Response to the outside world is slow, at 6 months of age, the baby still can not look at objects moving in the face, can not turn his head in the direction of the sound. 6.Language development is delayed, the baby can not babble at one year old, pronunciation is not clear. 7.Daily performance is abnormal, lack of interest in the surrounding people and environment. Lack of interest in the surrounding people and environment.