In the context of fundamental and comprehensive general education reform in Vietnam, STEM education competence among primary school teachers has become an urgent requirement to meet the demands of 21st-century student development. This study proposes a STEM education competency framework for students majoring in Primary Education, following the CDIO approach, aiming to guide curriculum development and assess the practical competencies of future teachers. Based on a synthesis of theoretical foundations, analysis of current conditions, and expert consultation using a two-round Delphi method (n=12), the research team developed a competency framework comprising five main domains: (1) STEM awareness and thinking; (2) Designing STEM educational activities; (3) Implementing STEM educational activities; (4) Applying technology and engineering in STEM education; and (5) Evaluating and improving STEM educational activities. Each competency domain includes two specific evaluation criteria, described across four developmental levels from basic to advanced. Expert evaluations indicate a high level of relevance and feasibility, affirming the framework's potential for application in training and assessing primary teacher education students with an emphasis on integrated and practical education.