Abstract: The weak principal-agent relationship is the root cause of the tension between doctors and patients. To solve the moral hazard of doctors, a principal-agent model was established to link the disutility of patients' medical expenses with doctors' salaries by drawing on the idea of "medical insurance integration". It is found that the greater the incentive coefficient in the salary system, the higher the efforts of doctors. The optimal incentive coefficient is different under different risk preference combinations. Internalized medical expenses largely avoid the moral hazard of "supporting medicine with drugs". On this basis, Rabin's reciprocity preference theory is introduced into the model to study the incentive mechanism design of doctor-patient transaction from the perspective of reciprocity. The results show that when the fixed fee paid by the patient is more than half of the maximum fixed fee that the patient can afford, and the effort of the doctor is more than half of the maximum effort, the doctor and the patient have reciprocal behaviors, and the benefits of both parties are higher than the benefits of complete rationality. At the same time, the higher the patient's fixed fee to the doctor, the greater the effort of the doctor. Finally, by comparing the benefits of patients and doctors under the condition of complete rationality and reciprocity preference through numerical simulation, it can be concluded that the benefits of patients and doctors under the condition of reciprocity preference have pareto improvement.