Abstract: Using the WISC R to judge two groups childrens IQ and the structure of intelligence. The test group included 47 children studied in special educational primary school (24 girls, 23 boys, aged from 8-11 years). The control group included 50 normal children (25 girls, 25 boys, aged from 8-11 years). All children were required to perform CATEGORY TEST. The result showed that there were significant differences in IQ between two groups. The IQ in the test group ranged from 46 69. So they could be diagnosed as Mental Retardation (MR). 14 MR children were out of balance between VIQ and PIQ. One child's PIQ was over 2SD higer than his VIQ. But the intelligence structures were very similar in two groups. There were siginificant differences on Category Test between two groups, and the result of Category Test was highly related to IQ (r=0.65). This indicated that Category Test could be used to test the thinking development of children.

Key words: mental retardation, children, intelligence quotient