Burnout and performance in multi-site physician practice: a dual-pathway model of policy and organizational support in China’s healthcare reform

China’s promotion of Multi-Site Practice (MSP) aims to redistribute medical expertise, yet its implications for physician well-being have received limited empirical attention. Using a sequential mixed-methods design grounded in the Job Demands–Resources (JD-R) framework, this study investigates the relationships among health policy, organizational support, job burnout, and job performance. Survey data were collected from 340 early-career physicians engaged in MSP across five elite tertiary hospitals in Zhejiang Province, complemented by semi-structured interviews with five senior experts. Structural Equation Modeling (SEM) was used to test a multi-level model, which demonstrated excellent fit (χ2/df = 1.118; CFI = 0.987; RMSEA = 0.019; SRMR = 0.029). The findings reveal a dual-pathway mechanism. On the impairment pathway, health policy significantly shaped hygiene factors, thereby intensifying job burnout (R2 = 0.83). On the motivational pathway, organizational support emerged as the strongest predictor of job performance (β = 0.59). Contrary to conventional assumptions, job burnout did not exhibit a significant direct effect on job performance (p > 0.05). The qualitative evidence indicates that the observed pattern results from a professionalism buffer, enabling doctors to continue their work despite significant stress. These findings suggest the need for policy and organizational interventions that prioritize physician well-being alongside performance.