The aim of this study is to investigate the effect of learning geometry topics of 7th grade in primary education with dynamic geometer's sketchpad geometry software to student's success and retention. The experimental research design with The Posttest-Only Control Group was used in this study. In the experimental group, dynamic geometer's sketchpad geometry software adapted to Computer assisted instruction; and in the control group, traditional teaching method was used. Quantitative research approaches were adopted in the study. Data was collected through 6th grade SFBS (state free boarding and scholarship) 2005 test, achievement test and worksheets. Mann Whitney U test and Wilcoxon signed-rank test were used to analyze the quantitative data of the study. As a result of this study, it was found that there was a significant difference between achievement test scores of experimental group learning geometry with GSP dynamic geometry software and control group learning through traditional method in favor of experimental group. (Contains 12 tables.)