Diabetes is characterised by hyperglycaemia resulted as the relative or absolute insulin deficiency which is closely related to islet beta cell failure. Apoptosis is the core mechanism of beta cell failure according to the studies on human islet. However, apoptosis can’t fully explain the loss of beta cell mass in the process of type 2 diabetes or the protective effect of early intervention. Recently, some other possible mechanisms of beta cell dysfunction have been proposed and dedifferentiation of beta cell draws extensive attention. Evidences of beta cell dedifferentiation in type 2 diabetes patients and animal models outlined and the transcription factors which determine beta cells of identity during this procedure are discussed in this review.