Three-year-old babies suddenly often wet their pants, may be related to psycho-psychological factors, may also be due to urinary tract infections, central nervous system diseases and other causes. 1. Spiritual psychological factors: for example, the child has been overly frightened in the near future, or just went to kindergarten, excessive emotional anxiety, may cause neurogenic urinary frequency, which may appear suddenly and often peeing pants. 2. Urinary tract infections: commonly found in cystitis, urethritis and other diseases, under the stimulating effect of inflammation, resulting in increased sensitivity of the urethral mucosa, which can easily cause urinary urgency, urinary frequency symptoms, it may suddenly appear often peeing in the pants phenomenon, which may be accompanied by urinary pain and other symptoms. 3. central nervous system disease: common in encephalitis, meningitis, etc., if not timely and effective treatment, is likely to damage the child’s control of urinary central nervous system, thus causing symptoms of enuresis, which can be manifested as a sudden and often peeing pants. Three-year-old baby suddenly often wet his pants, but also for other reasons, exclude mental psychological factors, it is recommended to take the child as soon as possible to see a doctor to diagnose the cause, by the doctor’s guidance for treatment and conditioning.