The study aimed at measuring effect of the use of the generative learning Model on achievement and geometric thinking for grade eight students in basic education. The researcher prepared tow tests:- The first one is testing the achievement and the other one is testing the ability to think geometrically throughout the first three levels i.e. visualization, analysis and informal deduction. The two tests have been verified for validity by a group of educators and have also been verified for reliability and calculating the internal consistency using-the method of Alpha Cronbach's, that reached (0.82) and (0.80) for the tow tests respectively. Sample of the study consisted of (59) students form the basic grade eight in Um Waraqa AL Ansari Basic Education School. They have been divided into two groups: experimental group which aimed to study the geometry unit using the generative learning Model and a control group which to study the same unit by a traditional teaching method. The two tests, the achievement test and geometrical thinking test, were applied upon the sample completing studying of the teaching unit. The results showed that the experimental group has exceeded the control group in both achievement and the geometrical thinking in the first three levels i.e. (visualization, analysis and analysis and informal deduction), throughout evidence of statistical differentiation at the level of significance (Q2 0.05) between the students' scores in the experimental and the control groups in the two tests. In light of this study, the researcher has provided many recommendations such as encouraging teachers to use the generative learning Model in teaching, taking care of developing levels of geometric thinking in mathematics using Van Heal Modeling. She also provided many suggestions such as studying the effectiveness of using the generative learning Model on other variables such as Mathematical proof.