Objective To explore the effect of a mobile platform for self-management of diabetes based on the COM-B model. Methods A total of 104 Mongolian sample of Northern China diagnosed with diabetes were randomized into a control group and an intervention group of 52, receiving either conventional health education or online intervention using a mobile platform for self-management developed based on the COM-B model. Results A total of 47 patients in the control group and 49 in the intervention group completed the study. After 6 months of intervention, the intervention group had better blood glucose control, higher self-management ability and self-efficacy compared with the control group (P<0.05,P<0.01). Conclusion Development of a mobile platform for diabetes self-management based on the COM-B model and implementation of online intervention, can achieve better blood glucose control and improve self-management ability.