Objective To explore the levels of serum 25(OH)D in glomerular disease patients and investigate its influence on the impaired glucose metabolism after treated with glucocorticoid. Methods A total of 61 patients with glomerular disease confirmed by clinical diagnosis and renal biopsy were included in the case group before receiving steroid therapy. 16 cases were selected as control at the same period. Before and six weeks after the treatment of glucocorticoid, all subjects took oral glucose tolerance test (OGT). According to the results of OGT, patients were divided into normal glucose regulation (NGR) group, impaired glucose regulation (IGR) group and steroid diabetes mellitus (SDM) group. Serum 25(OH)D levels were detected with enzyme?linked immunosorbent assay (ELISA), and other clinical data including albumin(Alb), Scr and urine protein were collected. Results (1) Before treated with glucocorticoid, the serum 25(OH)D levels in the control group [(64.09±13.53) nmol/L]were significantly higher than that in NGR group [(50.81 ± 12.44) nmol/L], while the latter was significantly higher than that in IGR group [(42.71 ± 8.09) nmol/L, all P<0.05]. In the glomerular disease patients, 18 cases (29.51%) were 25(OH)D insufficiency and 39 cases(63.93%) were 25(OH)D deficiency. 25(OH)D levels in patients with nephritis were significantly higher than in patients with nephroitic syndrome[(56.94 ± 10.41) nmol/L vs (45.88 ± 11.55) nmol/L, P<0.05]. (2)6 weeks after the treatment, incidence of steroid diabetes in IGR group was significantly higher than that in NGR group (61.11% vs 20.93%, P<0.05). Baseline levels of 25(OH)D in NGR group and IGR group were all significantly higher than that in SDM group [(55.68 ± 13.09) nmol/L, (48.97 ± 9.91) nmol/L vs (40.91 ± 7.82) nmol/L, all P<0.05]. (3)Serum levels of 25(OH)D were positively correlated with serum albumin and serum calcium, and negatively correlated with BMI, urinary protein, cholesterol and the 2 hours postprandial blood glucose. (4)Logistic regression analysis indicated that 25(OH)D<50 nmol/L and HbA1c>5.6% increased the risk of developing steroid diabetes 5.586 and 5.197 times, respectively. Age increased 10 years or insulin resistance index increased one, the risk of occurred SDM increased 2.443 and 2.755 times, respectively. Conclusions Most glomerular disease patients are serum 25 (OH)D deficiency or insufficiency. Low level of serum 25(OH)D is one of the main risk factors of steroid diabetes in patients with glomerular disease when treated with glucocorticoid.