Teacher self-efficacy is a key predictor of teaching effectiveness and student engagement, a concept that not only influences teaching quality but also directly affects student learning outcomes and development. In the Chinese educational context, teacher self-efficacy is affected by multiple factors, including excessive teaching workloads that limit teachers' capacity for pedagogical innovation, numerous non-instructional tasks that consume professional development time, and increasingly intense competition pressure that significantly impacts teachers' professional confidence. The purpose of this study is to investigate how participation in teaching competitions affects music teachers' self-efficacy.Based on this background, the study focuses on three core questions: (1) How do competition outcomes affect teachers' confidence? (2) What are the most important professional gains from the competition experience? (3) What challenges or confusion might teachers face after the competition? Methodologically, this study employs interview-based narrative research. Data collection revealed the following findings: (1) The high-intensity process of repeated lesson preparation significantly enhanced teachers' practical abilities in instructional design and implementation, with this substantial professional growth serving as an important source of confidence. (2) Competitions provided teachers with a platform to access cutting-edge educational concepts and innovative methods, broadening their professional perspectives while the high-pressure environment effectively strengthened their psychological resilience and adaptability. (3) However, excessive focus on competition rankings tended to trigger self-doubt and frustration when results fell short of expectations, potentially undermining teaching motivation. (4) Some teachers reported confusion about the significant disparity between meticulously polished "performance lessons" for competitions and the complex demands of routine classroom teaching, leading to doubts about their authentic teaching capabilities.The study concludes that teaching competitions function as a "double-edged sword." Depending on specific contexts and individual factors, they can either serve as a catalyst for teacher empowerment or as a source of pressure that undermines confidence. The research suggests that competition organizations should look beyond the contests themselves to build a more supportive and sustainable professional development ecosystem. This includes establishing diversified evaluation criteria and providing developmental rather than solely judgmental feedback. These measures will help maximize positive impacts, mitigate potential risks, and ensure that competitions genuinely serve the professional growth of all participating teachers.