The corona virus disease 2019 (COVID-19) is an epidemic pneumonia caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In addition to pulmonary symptoms and a variety of physical symptoms, patients also experience symptoms of cognitive impairment. Previous studies have shown that many patients will experience varying degrees of cognitive decline in the subacute and prognostic stages after having COVID-19. Then, what are the factors that lead to cognitive decline? This article reviews and analyzes the inherent factors before the onset of the disease, the factors directly related to the disease, and the factors of hospital admission. In addition, this paper also summarizes the evaluation methods of cognitive decline and the possible mechanisms of the pathogenesis, thus providing corresponding clinical intervention ideas for inhibiting or regulating related factors.