Background: In the elderly, diabetic retinopathy causes a significant deterioration in the functional activity and quality of life of patients, but the individual mechanisms of its development and, in particular, the influence of the components of the blood complement system remain insufficiently studied. The aim of the study: To analyze the features of the blood complement system in elderly patients with diabetic retinopathy. Materials and methods: The components of the blood complement system were studied in 78 patients aged 60-74 years with diabetic retinopathy (the main group) at the Tambov branch of the Academician S. N. Fedorov Eye Microsurgery Research Institute by means of an enzyme immunoassay and a hemolytic method using a commercial ELISA kit (UK). The control group consisted of 46 patients aged 60-74 years without diabetic retinopathy, in whom the blood complement system was similarly examined. To identify the leading components of the blood complement system that contribute to the development of diabetic. Results: In elderly patients with diabetic retinopathy, there was a significant and statistically significant increase in serum C3a components of the complement system to 145.9±4.3 ng/ml versus 43.1±3.8 ng/ml in the control group, C5a components to 6.8±0.4 ng/ml versus 3.2±0.2 ng/ml, respectively, factor H to 262.3±5.0 mcg/ml versus 139.8±4.1 mcg/ml. Simultaneously, with the development of diabetic retinopathy, a decrease in C1-ing components was observed. In accordance with the values of the odds ratio, the leading components of the blood complement system that determine the formation of diabetic retinopathy in old age are the C3a component, C5a component, and the H factor of the complement system. Conclusion: The results obtained in the scientific and practical aspect are of interest for understanding the etiopathogenesis of diabetic retinopathy and can be used in the development of treatment methods for this disease.