The promotion of cultural sustainability and cultural identity through the transmission of traditional music has become a prevalent theme in global music education. This instrumental case study, conducted in a capital city in south China (1) investigated the ways in which Chinese orchestra learning influences primary school students' cultural identity; (2) explored the developmental process of students' cultural identity in the Chinese orchestra. The research tools included observational field notes, reflective journals and semi-structured interviews. The participants were 32 primary school students and 5 music teachers. The findings suggested that the influences of the Chinese orchestra on the students' cultural identity were primarily due to the orchestra's cultural atmosphere and the elements of traditional instrumental music. Based on the four dimensions of cultural identity from a developmental perspective, this study further revealed the developmental trajectory of primary school students' cultural identity from behaviour to cognition to emotion and finally to evaluation during the period of Chinese orchestra learning. These findings contribute to a more comprehensive understanding of the role of music in shaping cultural identity and provide pedagogical implications for the effective promotion of cultural identity through traditional instrument learning.