Objective:To study preoperative concentrations of vitamin D in patients undergoing spinal surgery and analyze relevant risk factors associated with vitamin D deficiency. Methods:A retrospective analysis was conducted on 503 patients undergoing spinal surgery. Preoperative concentrations of serum 25-hydroxyvitamin D[25(OH)D]were measured. Normal vitamin D was defined as a serum 25(OH)D level ≥ 32 ng/mL,vitamin D insufficiency as 25(OH)D ≥ 20 and <32 ng/mL,and vitamin D deficiency as 25(OH)D < 20 ng/mL. Results:The rate of vitamin D deficiency and insufficiency was 71.4% and 23.9%,respectively. Rate of vitamin D deficiency in female patients was significantly higher than that in male patients (P < 0.001). Rate of vitamin D deficiency in patients with high body mass index (P = 0.009)or patients with smoking habit (P < 0.001)was much higher compared with that in the other patients. An analysis of monthly vitamin D levels revealed that rate of vitamin D deficiency was the lowest in September(44.8%),and the highest in January(90.6%). The analysis of quarterly vitamin D levels showed that rate of vitamin D deficiency was the lowest in winter and the highest in fall (P = 0.001). No correlation between vitamin D status with age or bone mineral density was identified. Multivariate analysis demonstrated that female(P < 0.001),smoking(P = 0.005),and winter(P = 0.001)were potential risk factors for vitamin D deficiency. Conclusion:Severe preoperative vitamin D insufficiency and deficiency existed in spinal surgery patients,and vitamin D insufficiency or deficiency may largely affect surgical outcomes of patients. Therefore,screening of preoperative vitamin D status and relevant treatment should be reinforced in spine surgery patients.