Abstract: Objective To investigate the correlation between vitamin D deficiency and endothelial dysfunction in patients with non-dialysis chronic kidney disease (CKD).Methods Patients with non-dialysis CKD and a stable clinical state were enrolled in this study. Vitamin D status of the patients was determined using serum 25-hydroxyvitamin D. Endothelial function was assessed by brachial artery flow-mediated dilation (FMD).Results Of 139 patients enrolled, there were 71 (51.08%) cases of vitamin D deficiency, 58 (41.73%) cases of vitamin D insufficiency and only 10 had normal vitamin D level. Patients with vitamin D deficiency and insufficiency had lower brachial artery FMD than patients with sufficient vitamin D level with the lowest level observed in vitamin D deficient group. Correlation analysis showed a positive correlation between FMD and 25(OH)D (r=0.623, P<0.01). The multiple regression analysis revealed vitamin D deficiency was an independent risk factor for endothelial dysfunction (β=0.418, P<0.01).Conclusions Vitamin D deficiency was associated with endothelial dysfunction in patients with non-dialysis CKD. Vitamin D supplementation may improve endothelial function in these patients.