The main aim of this study was to investigate the effect of Constructivist Learning Model (CLM) on Achievement and Creative Thinking in Chemistry among (11) Grade Students in General Learning, and also investigate and test the effect of sex on these tow variables. The sample of study consisted of (203) male and female students from the general Directorate of Education in Dhara North region. The Experimental group consisted of (52) male and (65) female students. The controlled group was represented by (25) male and (61) female students. Both groups studied the same unit in the chemistry syllabus, which was Thermal and Kinetic chemistry during seven weeks with a total number of (22) periods in the first semester for the academic year 2003/2004. An achievement test consisted of 30 was designed and used by the researcher, reliability of this test was (0.84) according to Cronbach Alpha. Also a test of Creative Scientific Thinking of sex activities which measured: Fluency, Flexibility and Originality was used. The reliability of this test was (0.90) according to Cronbach-Alpha. The validity of articles in this study was conducted through a panel of expert judges. The researcher also used statistical analyses besides means, stander deviation T-test. (ANCOVA) and Kendall's Coefficient to answer the questions of this study. The results revealed that them ware differences of statistical significance at the level (as0.01) between the two groups in the study in both variables: achievement and creative scientific thinking for the experimental group. The results also showed that there were differences of statistical significance at the level (a<0.01) between male and female in achievement variable for the female group. The study also revealed that there reaction between the method of teaching and sex at the level (as0.01) for the experimental group. According to these results and in the light of this study, the researcher made many recommendations for the education field and researchers to emphasize on (CLM) creative scientific thinking and them types and way of thinking.