Curriculum Based Measurement (CBM) is a supervision method of student’s educational achievement through direct assessment of predicted skills in the curriculum. Although almost half a century passes from the introduction of CBM in the world, however it has not been considered in Iranian curriculum. So, the aim of this research was to introduce and investigate the impact of CBM on math achievement of elementary students in comparison with conventional methods of formative evaluation. The present study based on the goal is applied research and in term of data collection is quasi experimental method with control group and pretest for a sample of 3rd grade elementary students. Results of Analysis of Covariance showed that CBM has significant effect on elementary students’ math achievement. Based on this research results, it is recommended that CBM is used in elementary curriculum as a more effective method of formative evaluation.