The most likely cause of urinary tract infection in 6-month-old babies is bacterial retrograde infection, followed by blood-borne infections, and then by urinary tract malformations. Infants and young children due to their own immunity is relatively low, coupled with the imperfect skin barrier system of infants and young children, bacteria are easy to enter the body with the urethra leading to urinary tract infections. In addition to this a small percentage of patients who have bacteremia can also cause blood borne urinary tract infections, especially upper urinary tract infections. If infants and young children have recurrent urinary tract infections, there may be a combination of urinary tract malformations, such as those caused by vesicoureteral reflux. Once an infant or young child has a urinary tract infection, he or she needs to go to the pediatrics department of the hospital to improve the urine routine, blood routine, and if necessary, improve the urinary tract ultrasound and other imaging tests, to make a clear diagnosis and then symptomatic treatment.