Mental retardation should be differentiated from the following diseases: 1. Temporary retardation of mental development: chronic physical diseases, post-disease weakness, malnutrition, taking sedative drugs or poor environment, lack of learning conditions, etc., can cause children’s reactive sluggishness and poor thinking, which can be easily misinterpreted as mental retardation and mental retardation. If their living and learning conditions are improved or after physical rehabilitation, their intelligence can be rapidly restored. 2.Epilepsy: Frequent epileptic seizures and the use of anti-epileptic drugs such as phenobarbital, carbamazepine and valproic acid can make the children sleepy, sluggish and similar to mental retardation. 3.Childhood schizophrenia: There can also be low academic performance, indifference, poor contact and adaptation to the surrounding environment, but most children do not have true mental retardation. 4.Visual and hearing impairment, so as to adapt to the environment and learning difficulties: early deafness severe people often have language development disorders, do not mistake these cases for mental retardation. Aphasia, dyslexia and dysgraphia caused by certain brain diseases also affect learning and language ability, but their general intelligence is good. 5, children with hyperactivity disorder: have inattention, poor academic performance, indiscipline, poor social adaptability and other characteristics, similar to mental retardation, but the examination of its intelligence is often within the normal range, the supervision of academic performance can be significantly improved, medication can be improved, these manifestations can be differentiated from mental retardation. 6, there are some normal children with slow development of speech and motor skills, but the general understanding and ability to adapt to the environment is still normal, once the functional development, can quickly catch up with the normal children, in all aspects do not appear to be lagging behind, and mental retardation is different.