The Research aimed to study the possibility of predicting working memory from cognitive flexibility and fluid intelligence, as well as to recognize differences between male and female in working memory and cognitive flexibility and fluid intelligence, and The relationship between these variables, The Research sample consists of (457) students in six grade elimantry school students,Working memory test and cognitive flexibility questioner prepared by researchers, and Coloured progressive matrices prepared by "Raven" to measuer fluid intelligence, had been applied, By using T-test , Product moment pearson and Regression analysis, The research found that: there are no differences between male and female in research varibles, It found also that there are not relationship between working memory and cognitive flexibility, but there are posative satistic relationship between working memory and fluid intelligence, working memory can be predicted from fluid intelligence.