Abstract: Diabetes is associated with the high risk of death of severe Coronavirus Disease 2019 (COVID-19), and the management levels of glycosylated hemoglobin (HbA1c) and blood glucose are also associated with the adverse outcomes of COVID-19. The proportion of newly diagnosed diabetes patients with COVID-19 is higher than that normal people, and severe patients may even cause diabetes ketoacidosis (DKA). In clinic, appropriate hypoglycemic regimen can improve the prognosis of COVID-19 patients. The relationship between COVID-19 and diabetes is complex. The article aimed to elaborate relevant studies and explore their relationship.