Whether or not a three-year-old boy with mental retardation can be cured depends on the specific development of the child, such as congenital causes may be completely cured probability is low. 1. congenital causes: children affected by genetic chromosomes, such as Down’s syndrome, then the possibility of returning to normal is very low, only to strengthen the child’s self-care ability training, to ensure that the child’s life can be self-care. 2. Acquired influences: If the developmental delay is caused by external factors or the child’s own physical developmental weakness, the need for timely intervention, repeated training, then the child’s hope of catching up with children of the same age is still great. The problem of mental retardation of three-year-old boy, must take the child to the regular hospital as soon as possible, first systematic examination, clear the cause of the child’s mental retardation, under the guidance of the doctor for treatment and regulation, the child’s mental retardation is expected to get a certain amount of recovery.