This study aimed to explore the improving role of glycine against induced diabetic retinopathy (DR) in experimental animals. Eighty-four female Wister rats were involved in the study. (1) The control group (C, n=21). (2) The glycine-supplemented group (G) with 10 gm/L in their drinking water (n=21). (3) Diabetic retinopathy group (DR) was intraperitoneally injected with STZ (n=21). (4) The treated group with glycine (DR+G) (n=21). The protein content, sodium dodecyl polyacrylamide gel electrophoresis (SDS-PAGE), and the damage to the DNA for retinal protein were evaluated after one week, two weeks, and four weeks, respectively. The elevation of protein concentration induced by DR were reduced by glycine and revealed a maximal decrease of 15.08% (P<0.05), 7.06% (P>0.05), and 2.05 %(P>0.05) after 1, 2, and 4 weeks, respectively. The protein structure was improved significantly by glycine and was indicated by the SDS-PAGE pattern. The damage in the DNA of retinal protein was enhanced by glycine after four weeks at the level of the number of tailed cells, tail length, the DNA% in the tail, and tail moment. Supplementing the amino acid glycine to an experimental model of rats with DR suggests therapeutic means for diabetic retinopathy by improving the retinal protein.