In the context of the implementation of the Vietnamese General Education Curriculum in 2018, teachers must be able to use knowledge from a variety of sources due to the demand to develop students’ competence. Teachers must transform it into knowledge to be taught and convert knowledge to be taught into taught knowledge. This process is related to the term called didactic transposition. To teach students, teachers need to be adept at didactic transposition. The study aims to propose a set of criteria for the internal didactic transposition competence, surveying the internal didactic transposition competence of mathematics preservice teachers presently training at Hanoi National University of Education, and suggesting some measures to enhance that competence.