This study aimed to investigate the intermediating role of self-regulation in the relationship between mathematical educational beliefs and students' math anxiety. The descriptive method was correlation sort which is based on structural equations. The statistical subjects of this study were selected from 2710 male students in the ninth grade of secondary school in public schools in the 4th district of Tehran in the educational years 2020-2021. In this study, 300 students were chosen by a two-step cluster method as the sample size, to collect data, Plake and Parker’s Math Anxiety Questionnaire (1982), Ledder & Forgasz’s Math Educational Beliefs Questionnaire (2002), and Sawari & Arabzadeh’s Self-Regulation Questionnaire (2013) were applied. Structural equation modeling(SEM) with SPSS 18 and AMOS23 were used to analyze the data. The findings showed that math educational beliefs and self-regulation have a direct effect on students' math anxiety (p<0.01)., and mathematical educational beliefs have an indirect effect on math anxiety with mediating of self-regulation (p<0.01), and the research model was approved. This study shows the importance of educational cognitive elements in math anxiety and it is suggested that the educational systems set plans to improve students' positive educational and cognitive beliefs and as a results decrease anxiety in educational settings especially math anxiety.