In the context of current educational innovation with an increase in the use of mathematics to solve real life problems, the application of the theory of Realistic Mathematics Education (RME) in teaching mathematics is appropriate and feasible. This article provides an overview of the RME theory and its application in teaching mathematics.Based on this theoretical framework, we compare the ways of the introduction of the function in the Vietnamese and American textbooks. The results of the analysis show that with the use of the RME approach in teaching this function in the American textbooks, students are involved in the process of re-inventing knowledge, recognizing the role of mathematics in real life, and have opportunities to develop critical thinking and problem-solving capacities. We then propose further studies so that we can deploy the quadratic function teaching in Vietnam using the RME approach.