Research objective: This study is designed towards the goal of assessing the actual situation of applying metacognition in the process of teaching and learning Mathematics in secondary schools, then, proposing appropriate measures for developing mathematical competence. Research method: In this study, we conducted a survey by using questionnaire, observation, in-depth interview. The survey was conducted at 5 secondary schools in Tuyen Quang province (Y La Secondary School; Phan Thiet Secondary School; Hung Thanh Secondary School, Le Quy Don Secondary School, and Nong Tien Secondary School). Survey subjects include: 7 education experts, 30 teachers of Mathematics at secondary schools, 100 students in 9th grade. After obtaining survey data, we used mathematical statistical methods to calculate the percentage for each level. From there, make comments and suggestions. Survey period: January 2020 to April 2020. Research results: research showed that there was a percentage of teachers and students who apply metacognition in the teaching and learning process. However, the activities of applying metacognition in both teachers and students are not regular, there is no habit of using metacognition as a thinking tool. Therefore, students' results have not made significant progress in math ability, as well as low learning outcomes in Math. In the last part, the study suggested 4 measures for applying metacognition in the process of teaching and learning Mathematics, aiming to develop students' mathematical ability

Metacognition, Mathematical Competence, Mathematical Thinking.