Self-care is important for type 2 diabetes mellitus (T2DM) patients' disease prognosis, but there is a common phenomenon of self-regulation failure in T2DMs. In order to figure this problem out, the current study explored the interaction between self-regulation resource depletion and diabetes self-care based on the limited resource model of self-regulation. 104 patients were surveyed using the Self-Regulatory Fatigue Scale (SRF-S) and the Diabetes Self-care Scale (DSCS) in study 1. Study 2 recruited 30 T2DM patients and 30 healthy controls, and used a sequential-task paradigm to test the effect of self-regulation resource depletion on them. Participants in study 3 were 60 T2DM patients under different levels of self-regulation resource depletion manipulation, and their self-regulation performance was recorded and compared. Study 1 indicated that the correlation between self-regulation resource depletion and exercise and diet was significant and negative, suggesting that patients with greater self-regulation resource depletion performed poorly in exercise and diet. In Study 2, T2DM patients exhibited a poorer performance on the Spatial Incompatibility Task than the participants in the control group, suggesting that their self-regulation resource was insufficient. Study 3 indicated that there was no difference in Spatial Incompatibility Task performance, reaction time or error number among patients who were requested to complete a dietary record for one week and patients who were only requested to record eating times. This research demonstrated that low levels of diabetes self-care execution was associated with patients' deficiency in self-regulatory resource, and self-care as a series of goal-directed behaviors consumed patients' self-regulatory resources before these behaviors became a habit.