Infants are in the infantile stage at three months, when physical and neurological development is faster. The infant’s birth weight is usually 3.25kg, and in the 3rd to 4th month the weight is about twice as much as that at birth; the height grows faster in the first 3 months to about 11~13cm, and the head circumference grows faster. At 3 months, the spine begins to curve, head-up movement appears, cervical vertebrae are convex; the wrist cephalic bone and hook bone begin to appear ossification center, the grip reflex begins to disappear, the muscle tone is higher, the supine position can be changed to prone position, can use the hand to touch things, can babble to pronounce the sound, the head can be rotated 180 ° with the objects seen or the sound heard, and like to notice their own hands. Infants at 3 months are in a critical period of physical and neurological development, at this time should pay attention to the baby’s mood, maintain balanced nutrition, pay attention to warmth, avoid cold.