The retina is a light-sensitive membrane responsible for optical signal reception and concatenation with the optic nerve. Retinal damage causes blurred vision or visual dysfunction. Diabetic retinopathy (DR) is a common microvascular complication of diabetes mellitus (DM) that is induced by the interaction of multiple factors and mechanisms. Hyperglycemia and hypertension are potential risk factors for DR. With the growing number of DM patients, the incidence of DR increases if DM is untreated. Epidemiological data show that DR is a leading cause of blindness in working-aged adults. Regular ophthalmological check-ups, laser treatment, and interdisciplinary consultation for reducing visual atrophy can help prevent and treat DR. Although the pathogenesis of DR is complex, and the exact pathological mechanism of DR needs to be further elucidated to promote new drug research and development against DR. The entire pathological process of DR involves increased oxidative stress (microvascular dysfunction, mitochondrial dysfunction) and chronic inflammation (inflammatory infiltration, cell necrosis) and impairment of the renin-angiotensin system (microcirculation dysregulation). This review aims to summarize the pathological mechanisms underlying the development of DR to improve clinical diagnosis and effective treatment of DR.