This study aimed to discover the effectiveness of using metacognition strategies on achieve of mathematics and developing reflective thinking for class nine in basic education. To achieve this we have prepared guidebook for the teacher in the unit of the equations and functions according to metacognition strategies. The researcher has prepared two tests, the first in achievement, and the second in reflective thinking and after that Measured for validity and reliability of them. Sample of the study consisted of (60) students from grade nine selected from basic education schools in Al-Dhahra educational governorate, they have been divided into two groups: experimental group who studied the unit of the equations and functions using metacognition strategies and a controller group who studied the same unit by a traditional teaching method. The study result show that: . There is a statistically significant difference at the level of significance (a < 0.05) between the mean score of the experimental group and the mean score of the control group in the post achievement test for the favor of the experimental group. There is a statistically significant difference at the level of significance (a < 0.05) between the mean score of the experimental group and the mean score of the control group in the post reflective thinking test for the favor of the experimental group. The study ended with some recommendations such as encouraging teachers to use metacognition strategies in teaching and taking care of developing reflective thinking skills in mathematics. They focus on the use of modern teaching methods and didn't use traditional methods that focus on memorization and indoctrination.