Children’s sudden urinary frequency may be physiological frequent urination, urinary tract infection, bladder lesions and other causes. 1. Physiological urinary frequency: cold days or drinking too much water can cause frequent urination, urination, in addition to children’s bladder storage capacity is small will also appear frequent urination. 2. Urinary tract infection: urethral mucosal epithelial cells are invaded by pathogens, urethral mucosal epithelial cells will be damaged. Urine stimulates the nerves in the damaged cells during urination, causing symptoms such as frequent urination, urinary urgency, and painful urination. 3. Bladder lesions: bladder stones, urinary tract stones stimulate the bladder triangle, bilateral ureteral end of the stone embedded stimulation of the bladder triangle, easy to bladder irritation symptoms. Make the child appear urinary frequency, urinary urgency, urinary pain symptoms. When the child suddenly urinate frequently it is recommended to go to the hospital urology department for examination and treatment according to their own condition.