Professional identity development (PID) of school music teachers is critical to teacher community sustainability, the quality of school music practices, and the long-term well-being of the music education system. While in-service music teacher training strengthens the occupational aspects of teachers' identity, the iterative PID process is both content-dependent and context-dependent. Using a framework based on the Surveys of Enacted Curriculum (SEC), this study explored school music teachers' PID profiles in Mainland China after a 10-year implementation of the National Teacher Training Program (NTTP). Prominent characteristics of teachers' PID were analysed regarding self-efficacy, belief, professional commitment, and task orientation, relating to self-report and observed classroom instructional practices. Statistical analysis showed high coverage of curriculum content in teachers' daily instructional practices, while minor differences are evident among groups by region, grade band, and years of teaching. The impact of NTTP on PID and implications for in-service music teacher training are discussed.