3-year-old female baby has secretion under the lower side, may be physiological and pathological factors, pathological factors can be related to vulvovaginitis. 1. physiological factors: children in the process of growth and development as well as daily activities, perineum may have a small amount of discharge, but no local pain, redness and swelling, parents pay attention to the timely change of underwear, to maintain local cleanliness. 2. Vulvovaginitis: at the onset, there is vaginal purulent secretion, secretion stimulation of the vulva can cause local pain and itching, infants and young children have more than crying or scratching performance. 3 year old baby girl with discharge, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.