Objective To explore the relationship between the classification of diabetic macular edema（DME）and the stages of the diabetic retinopathy (DR) , the diabetic duration and the visual loss.Methods Retrospectively analyzed the clinical data of fundus fluorescein angiography (FFA) and other related information of 1521 patients who were diagnosed as DR. Classified DR according to national standard of the diagnosis and classification of DR, and classified DME according to the standard made by the early treatment diabetic retinopathy study research group of United States. The occurrence of DME in DR in each stage and the relationships between DME and the disease course and the vision were analyzed.Results In 1521 patients, 791 eyes in 468 patients had DME ( 30.77%), including 361 eyes (45.64%) with focal DME and 430 eyes (54.36%) with diffuse DME. The occurrence of DME was 1.13% in I-stage DR, 7.84%in II-stage DR, 41.98% in III-stage DR, and 48.93% in IV-stage DR. Focal and diffuse DME usually occurred at the III and IV stage of DR respectively, with 178 eyes (22.51%) with focal macular edema at the III stage of DR, and 249 eyes (31.48%) with diffuse DME at the IV-stage of DR. Patients with DME were hardly found at the V and VI stage of DR because of retinal proliferation and vitreous hemorrhage or other complications which made the condition of macula region blurred. The visual acuity of diffuse DME was worse than focal DME. DME often occurred within 10 years in the diabetic duration, and its severity and incidence increased year by year.Conclusions DME is the main cause of visual impairment of DR. The incidence of DME increased as the course of the DR prolonged. Along with the development of retinopathy, the incidence of DME increased, and the severity of DME aggravated, but the development of DME and its classification can not be brought into definite correspondence or unification with the classification of DR, hence the typing of DME in another individual classification in DR is of course necessary. (Chin J Ocul Fundus Dis，2003，19：83-86)