Objective:To explore the driving mechanisms of doctors′ collaborative willingness and behavior in the tiered diagnosis and treatment system, in order to provide reference for promoting the construction of the tiered diagnosis and treatment system.Methods:Based on the harmonious management theory, a theoretical framework for the driving mechanisms of doctors′ collaborative behavior in the tiered diagnosis and treatment system was developed. Through random sampling, a questionnaire survey was conducted among doctors from 40 medical institutions in five prefecture-level cities in Zhejiang province between April and May 2022. The t-test, variance analysis, and non-parametric tests were employed to analyze the differences in collaborative willingness and behavior among doctors based on various demographic characteristics. The structural equation model and stratified linear regression were used to assess the impact of collaborative factors (professional environment and work expectations) and harmonious factors (perception of policy support and perception of management mechanism) on doctors′ collaboration willingness and behavior. Results:A total of 1 959 doctors participated in the survey. Doctors′ collaborative behavior scored 2.13±1.12, indicating a slightly below-average level, whereas their willingness to collaborate scored 3.88±0.79, falling between neutral and somewhat willing. Significant differences in collaborative behavior scores were observed based on the medical institution′s ranking, age, years of experience, monthly average income, and professional titles ( P<0.05). Both collaborative and harmonious factors directly influenced the doctors′ willingness to collaborate, with standardized path coefficients of 0.428 and 0.139, respectively. Similarly, these factors directly impacted their collaborative behavior, with standardized path coefficients of 0.104 and 0.366. The perceptions of policy support and management mechanisms demonstrated a significant positive moderating effect on the relationship between doctors′ collaborative willingness and behavior, with effect values of 0.047 and 0.043 respectively ( P<0.05). Conclusions:The collaborative and harmonious elements serve as positive drivers for collaboration among doctors in the tiered diagnosis and treatment system at both the cognitive and behavioral levels. Enhancing and optimizing policy support and management mechanisms can facilitate the transition from intention to actual collaborative actions among doctors from different levels of medical institutions.