Objective To explore the influence of expressive writing of positive emotions on stigma in young and middl-aged patients with type 2 diabetes mellitus (T2DM). Methods Totally, 100 young and middle-aged T2DM patients were randomly divided into 2 groups of 50 cases each. The control group received routine nursing care, while the intervention group additionally received expressive writing of positive emotions. The intervention lasted for 8 weeks. The two groups were assessed with Type 2 Diabetes Stigma Assessment Scale (DSAS-2), Diabetes Management Self-efficacy Scale (DMSES), World Health Organization-5 Well-being Index (WHO-5) before and after the intervention. Results Forty-five patients in control group and forty-seven patients in intervention group completed the study. After intervention, the scores of stigma were significantly lower, while the scores of self-efficacy and well-being were significantly higher, in the intervention group than those in the control group （P＜0.05 for all）. Conclusion Expressive writing of positive emotions in young and middle-aged T2DM patients with stigma can significantly reduce stigma level of patients, and improve patients′ disease management self-efficacy and subjective well-being.