Background China's primary health care system is advancing family doctor contract services, aiming to provide integrated and continuous services for residents, which are essential characteristics needed by chronic disease patients such as those with diabetes. Existing studies have largely focused on descriptive analyses of the coverage rate of family doctor contract services, with insufficient assessment of their actual effects in chronic disease services. Objective To understand the impact of family doctor contract services on the cognition, behavior, and health outcomes of diabetic patients. Methods From February 22 to 25, 2023, a multi-stage stratified random sampling method was used to survey 716 registered diabetic patients in a city in Shandong Province. The questionnaire included demographic information, disease and medical conditions, acceptance of diabetes management services, and patients' disease cognition, health management behaviors, and health outcomes. Descriptive analysis was conducted on the coverage rate of diabetes management services accepted by patients to reflect the integration of family doctor team services. Multifactorial Logistic regression analysis was used to explore the impact of contracting with a family doctor on patients' disease cognition, health management behaviors, and health outcomes. Results The contract rate of diabetic patients was 80.9% (579/716). Among them, 47.8% (277/579) felt that the family doctor understood their psychological condition.The rate of receiving follow-up recently was 89.8% (643/716). Among them, 76.0% (489/643) received diabetes health education, and 43.9% (282/643) received the complication-related examination items such as fundus, ECG, and dorsalis pedis artery pulsation. Of the patients with sudden worsening/acute complications, 37.7% (32/85) contacted the family doctor, among which 37.5% (12/32) received emergency treatment, and 25.0% (8/32) received referral services. The correct rate of patients' cognition on diabetes diagnosis was 19.8% (142/716), and the correct rate of cognition on intervention methods other than drug treatment was <70.0%. The results of the multifactorial Logistic regression analysis showed that the probability of contracted patients having a disease cognition score >5.5 was higher [OR (95%CI) =1.80 (1.23-2.62), P<0.05], the probability of undergoing glycosylated hemoglobin testing was higher [OR (95%CI) =2.67 (1.75-4.18), P<0.05], the probability of regular self-monitoring of blood glucose was higher [OR (95%CI) =4.28 (2.57-7.09), P<0.05], the probability of dietary control was higher [OR (95%CI) =0.46 (0.28-0.80), P<0.05], and the acceptance rate of diabetes-related expenses was lower [OR (95%CI) =1.58 (1.04-2.39), P<0.05] . Conclusion Family doctor contracted services have shown a significant impact on enhancing the quality of management services for chronic diseases. However, there is still a need for further improvement in implementing patient health education and psychological care components within the service package. Establishing a robust referral mechanism and improving the screening of diabetes complications are essential steps towards enhancing these services. Meanwhile, greater attention should be given to the health services of patients who have not enrolled in the contracted services.