Science, technology, engineering, arts, and mathematics (STEAM) has gained increasing attention for its potential to enhance student learning experiences, critical thinking, and problem-solving skills. However, implementing STEAM in mathematics education presents numerous challenges. This study examines the factors that influence mathematics teachers' willingness to adopt STEAM by integrating the Theory of Planned Behavior (TPB) and the Technology Acceptance Model (TAM) with an innovative component STEAM literacy. Utilizing questionnaire data from 1,173 mathematics teachers across China and employing Structural Equation Modeling (SEM), our analysis highlights the critical roles of perceived usefulness and subjective norm in motivating teachers' intentions to engage with STEAM. Furthermore, we find that these intentions significantly predict actual implementation. Notably, the inclusion of STEAM literacy within the TPB-TAM framework offers a unique perspective, demonstrating that enhancing STEAM literacy, alongside fostering positive attitudes and providing adequate resources, can significantly influence both the intention and the practical adoption of STEAM education. This study delivers valuable insights for educational policymakers and practitioners on promoting STEAM effectively.