The purpose of this paper is to evaluate the reality of teaching and learning with the support of a calculator, examine the benefits and challenges of using a calculator in teaching mathematics in high school. The study is based on the survey data from math teachers, educational managers, and students who were selected from 24 high schools in seven provinces representing different regions of Vietnam. Initial research results show that using calculators for teachers and students in teaching and learning mathematics has been widely developed in recent times in Vietnam, especially since the implementation of the curriculum general education 2006. Calculators can support from knowledge discovery, conceptual approach to problem solving. For teachers, calculator have a positive impact on the views and attitudes of information technology applications in teaching, promoting innovation of teaching and learning methods. However, many teachers and educational managers used to worry about using calculator like affecting the students' computing skills and hindering the goal of developing mathematical thinking. In terms of organizing teaching with calculators, the main difficulties are uneven equipment, lack of teaching documents, and no mechanism on financial support teachers and students.