Retinal vascular bed area(RVBA)is the total area of retinal vasculature segmented by ultra-widefield fluorescein angiography(UWFA)images, and is an objective absolute value in square millimeter. RVBA is mainly affected by the diameter and length of retinal vessels, and whether RVBA increases or decreases depends on the “competition” between ischemia and angiogenesis, indicating subtle changes in retinal vascular morphology. As a new indicator for the study of retinal vascular diseases, RVBA may have higher stability and accuracy than the ischemia index(ISI)and non-perfusion area(NPA). RVBA is currently mainly used to evaluate the progression and prognosis of diabetic retinopathy(DR). It was found that retinal total RVBA in DR eyes was greater than the normal eyes and it decreased in DR eyes after anti-vascular endothelial growth factor(VEGF)treatment. These findings provide favorable support for the study of microvascular lesions in DR. In this article, the application of RVBA in DR was reviewed to provide a reference for the clinical study of RVBA in other retinal vascular diseases such as retinal vein occlusion(RVO).