This study aimed to evaluate the diagnostic ability and sectoral structure function relationship of circumpapillary vessel density (cpVD) and macular vessel density (mVD) with optical coherence tomography angiography (OCTA) in early glaucomatous (EG) eyes. 224 EG eyes of 167 patients (mean deviation (MD) > - 6 dB) and 70 normal eyes of 70 subjects were enrolled in this retrospective cross-sectional study. All patients underwent OCT and OCTA scanning. Diagnostic abilities were evaluated with area under receiver operating characteristic curves (AUROC). Structure function relationships of superior, inferior and Garway-Heath sectoral values with its corresponding visual field (VF) sensitivity were determined using linear mixed models. AUROCs were 0.798, 0.621, 0.876 and 0.835 for cpVD, mVD, circumpapillary retinal nerve fiber layer thickness (cpRNFLT) and ganglion cell-inner plexiform layer, respectively. AUROC of cpVD was significantly lower than cpRNFLT (P = 0.010) and higher than mVD (P < 0.001). All Garway-Heath sectors of cpVD significantly correlated with its corresponding VF sensitivity except for the nasal sector. MVD also showed significant structure function relationship and the correlations were stronger in the perifoveal region (6 mm annulus) than in the parafoveal region (3 mm annulus). CpVD demonstrated moderate diagnostic ability and both cpVD and mVD demonstrated significant association with VF sensitivity in EG eyes.