To investigate the mechanism of self-efficacy between self-management ability and self-management behavior and its differences among patients with different disease courses through mediation tests.In the study, 489 patients with type 2 diabetes who attended the endocrinology departments of four hospitals in Shanxi Province and Inner Mongolia Autonomous Region from July to September 2022 were enrolled as the study population. They were investigated by General Information Questionnaire, Diabetes Self-Management Scale, Chinese version of Diabetes Empowerment Simplified Scale, and Diabetes Self-Efficacy Scale. Mediation analyses were performed using the linear regression model, Sobel test, and Bootstrap test in the software Stata version 15.0 and divided the patients into different disease course groups for subgroup analysis according to whether the disease course was > 5 years.In this study, the score of self-management behavior in the patients with type 2 diabetes was 6.16±1.41, the score of self-management ability was 3.99±0.74, and the score of self-efficacy was 7.05±1.90. The results of the study showed that self-efficacy was positively correlated with self-management ability (r=0.33) as well as self-management behavior (r=0.47) in the patients with type 2 diabetes (P 5 years, the mediating effect accounted for 39.20% of the total effect.Self-efficacy enhanced the effect of self-management ability on the behavior of the patients with type 2 diabetes, and this positive effect was more significant for the patients with shorter disease course. Targeted health education should be carried out to enhance patients' self-efficacy and self-management ability according to their disease characteristics, to stimulate their inner action, to promote the development of their self-management behaviors, and to form a more stable and long-term mechanism for disease management.