The purpose of this study is to analize, to compare the Down` Syndrom Children by the developmental characteristics of visual perception of mental age and separate subtests. It is calculated upon, therefore, above the two group`s tendency of the reaction by perceptual age(PA). The subject of this study is 80 of the Down` Syndrom (IQ 50-70) at the special school for the mental retarded and also 80 of the normal children (IQ 90-110) at nursery school, kindergarten, and elementary school in Seoul. Their PA is measured by the DTVP(Developmental Test of Visual Perception). The results of this study are as follows : The first, it is shown differential characteristics between the Down` Syndrom group and the normal children group ; that is, the latter is almost approached the high level of visual perception at MA 9 years old, the former is delayed at 1-2 years old in all students of DTVP. It is shown that the two groups are indifferent developmental from VM(Visual -Motor Coordination) area at MA 3 years old; the Down`s Syndrom group`s children are more retardation than normal children about one year at FG(Figure-Ground Discrimination), PC(Perceptual Constancy), PS(Position in Space), SR(Special Relationships) area, etc. and especially it is shown delay at the PC area. The second, it is revealed that the Down` Syndrom group are informed quickly visual perception development at the mental age 5-7 years old, but normal group are informed clearly visual perception development at the mental age 3-5 years old. There are some characteristics among the subtests; that is, at the Down`s Syndrom group, it is retarded about 2 years old at the PC area more than normal children gorup. Thus it is shown that the latter is very lower the abstract ability than the former.