Objective: Based on the KAP and Prospect theory, to explore, construct and verify the theoretical model and formation mechanism of driving factors of primary care doctors′ willingness to carry out the primary diagnosis. Methods: Using the random cluster sampling method, from April to May 2019, a questionnaire survey was conducted among doctors at 20 primary medical and health service institutions in Hangzhou. The survey covered the primary care doctors′ cognition level of primary diagnosis, their self-evaluation of primary medical care capabilities, evaluation of policies and systems, expectation of primary medical care, and their job satisfaction. Descriptive statistic, multiple linear regression and structural equation model were used to analyze and explore the driving factors and formation mechanism of their willingness to carry out the primary diagnosis. Results: Primary care doctors′ willingness rate for primary diagnosis was 76.4%(308/403). Positive expectation(beta=0.309), cognition level(beta=0.216), evaluation of policies and systems(beta=0.184), and self-evaluation of primary diagnosis capability(beta=0.170), all of which directly affect the said willingness. The total effect of the five types of driving factors on the willingness of the primary diagnosis was as follows: cognitive level of the primary diagnosis(0.536), evaluation of the policy system(0.494), self-evaluation of the primary diagnosis capability(0.436), positive expectations of the primary diagnosis work(0.186), job satisfaction(0.146). Conclusions The cognition of the primary diagnosis, the capability of the primary diagnosis, the policy system and the positive expectation are the important premises, key driving forces, and a strong guarantee and motivation to drive primary care doctors to carry out the primary diagnosis. It is suggested that the government and medical institutions should further improve the cognition level of primary care doctors, focusing on systematically improving the service capability of primary care doctors′ primary consultation, coordinating to improve policy guidance measures such as financial input, medical insurance reimbursement and referral system, establishing and improving incentive measures such as career development, performance appraisal, salary and welfare of primary care doctors.