11-year-old boy with small black fuzz on the mouth is a normal phenomenon that children will grow a beard after entering puberty. 11 year old boy generally speaking has begun to gradually enter puberty, male secondary sexual characteristics will gradually appear under the stimulation of androgen, such as the emergence of laryngeal knots, voice, sweat and other hair increase, penis development and other physiological phenomena. The 11-year-old boy appeared on the mouth of the small black velvet hair is also a normal physiological phenomenon, with the growth of age, these small black velvet hair will gradually become black hard hair, commonly known as “beard”. So during the youth, 11-year-old boys first need to supplement adequate nutrition, increase milk and other protein-rich food intake, to ensure their own rapid growth and development.