Objective To investigate the correlation between the thickness of retinal nerve fiber layer (RNFL) and dietary fat in patients with type 2 diabetes mellitus (T2DM). Methods A total of 186 in-patients with T2DM admitted to our department were selected for the study. Their general clinical data were retrieved, including age, gender, disease course, previous history, smoking and drinking history, admission blood pressure, height, and body mass, and body mass index (BMI) was calculated. Blood test results such as glycosylated hemoglobin A1c, fasting C-peptide, blood lipid and kidney function were recorded, and RNFL thickness was measured by optical coherence tomography. A semi-quantitative dietary frequency questionnaire was conducted with each participant. SPSS statistics 22.0 was used for statistical analysis, and Spearman rank correlation analysis for correlation between RNFL thickness and dietary fat mass. The univariate and multivariate linear regression analysis were performed to explore the independent influencing factors of RNFL thickness in each quadrant of both eyes. Results (1) Livestock and poultry meat and meat products were significantly negatively correlated with the superior and inferior RNFL thickness (superior:r=-0.192, P=0.009; inferior:r=-0.286, P=0.000). Soft drinks were significantly negatively correlated with the superior and inferior RNFL thickness (superior:r=-0.169, P=0.021; inferior:r=-0.264, P=0.000). There was a significant negative correlation between serum triglycerides (TG) and the inferior, nasal RNFL thickness (inferior:r=-0.210, P=0.004; nasal:r=-0.150, P=0.041). Serum creatinine (SCr) was negatively correlated with the superior and nasal RNFL thickness (superior:r=-0.159, P=0.032; nasal:r=-0.156, P=0.036). Age was also negatively correlated with the superior, nasal RNFL thickness (superior:r=-0.169, P=0.021; nasal:r=-0.184, P=0.012). (2) Univariate linear regression analysis showed that age, TG, SCr, poultry meat and meat products were associated with RNFL in patients with T2DM (P＜0.05). On the basis of the above univariate linear regression, multivariate linear regression was performed with RNFL thickness in each quadrant of T2DM patients as the dependent variable and age, TG, SCr, poultry meat and meat products as the independent variables, which showed that TG (P=0.007), poultry meat, and meat products (P=0.021) as independent influencing factors for the inferior RNFL thickness; age (P=0.013) and TG (P=0.044) for RNFL thickness in the nasal quadrant; and SCr (P=0.042) for the RNFL thickness in the temporal quadrant of the eye. Conclusion The intake of livestock and poultry meat and meat products is closely related to the thickness of RNFL in the patients with T2DM, and dietary intervention has clinical significance for early prevention of T2DM retinopathy.