Objective To analyze the application value of optical coherence tomography angiography (OCTA) in the diagnosis of non-proliferative diabetic retinopathy (NPDR). Methods A total of 122 patients with or without diabetic retinopathy who has the history of diabetes mellitus were consecutively enrolled from January 2021 to June 2023. All the patients were examined with fundus fluorescein angiography (FFA) followed by OCTA. According to the results of FFA, the patients were divided into four groups: control（non-OCTA）, mild, moderate and severe NPDR groups. OCTA indice included central macular thickness（CMT）， vascular density (VD), perfusion density (PD), foveal avascular zone area(FAZ-A), foveal avascular zone perimeter (FAZ-P), and foveal avascular zone circularity index (FAZ-CI) along with central macular thickness (CMT). The differences in quantitative levels of OCTA parameters were assessed with one-way analysis of variance or non-parametric test, and the risk for NPDR development and severity by OCTA parameters were evaluated with multiple Logistic regression modeling analysis.The diagnostic values of single OCTA parameter or in combination for NPDR were evaluated with receiver operating characteristic (ROC) curve and area under curve (AUC) analysis methods. Results VDs in the NPDR groups were significantly lower than that of control group, showing obvious decrease in severe NPDR group compared to the mild and the moderate groups (P<0.05). PD in moderate and severe NPDR groups were significantly lower than that of control group (P<0.05). PD in severe NPDR group was lower than those of mild and moderate NPDR groups. FAZ-A in the mild, moderate and severe NPDR groups were significantly lower than that of control group (P<0.05), but no difference was observed among the three NPDR groups. FAZ-P in the mild, moderate and severe NPDR groups were significantly lower than those of control group (P<0.05), but no difference was observed among these NPDR groups. There was no statistical difference in FAZ-CI between groups. Multiple logistic regression analysis showed that CMT increase, VD and FAZ-P decrease were accociated with NPRD (P=0.03, <0.001 and 0.001), while CMT increase and VD decrease were independent risk factors for NPDR severity (P=0.01, <0.001). ROC curve analysis showed that CMT(>260.00 μm), VD (<16.55/mm²) and FAZ-P (<2.15 mm) were of significant independent diagnostic value for NPDR (AUC=0.63, 0.78 and 0.70), among which the diagnostic efficiency of VD was significantly higher than that of CMT (P=0.02), and no statistical difference of diagnostic efficacy between CMT and VD or FAZ-P (P>0.05). A combination of CMT, VD and FAZ-P showed higher diagnostic value than any single measurement (AUC=0.86, all P <0.05). Conclusions The OCTA parameters CMT, VD and FAZ-P alone show significant independent diagnostic values for NPDR, and combination of three indices have more efficacy.Integrating the vascular parameters with macular morphology of OCTA measurement might effectively improve clinical diagnosis of NDPR.