The study aims to identify the effectiveness of using (Moodle) system in teaching mathematics on post and retention achievement of the ninth Grade students. The study sample consisted of (63) female students. They were divided into two groups: an experimental group consisted of (32) students, and a controll group (31) students. To achieve the objectives of the study the researcher used an achievement test of (20) multiple choice items with four alternatives. Later on, the validity of content was verified by presenting it to a group of measurement, evaluation and curriculum and instruction .The reliability was also determined by implementing it on a random sample consisting of (30) students, and Chronbachs Alpha coefficient for internal consistency was calculated which gave the value of (0.71). To answer the questions of the study the averages, standard deviations and the "t-test" were calculated by using the statistical program (spss). The main finding of this study is: there was a statistically significant difference at the level of (a = 0.05) between the averages of the experimental and the control groups in both post and retention achievement tests in favor of the experimental group. According to the study results, the researcher recommends that: there is a need to use the (Moodle) system in the teaching of mathematics.