Objective · To investigate the correlation between serum 25-hydroxyvitamin D [25(OH)D] level and leukoaraiosis (LA). Methods · A total of 170 patients with LA who underwent treatment in the Department of Neurology in Wuxi Fifth Peoples Hospital Oct. 2017 to Oct. 2018 were enrolled. Their general clinical data were collected and the serum 25(OH)D levels were measured. Head cerebral magnetic resonance imaging was performed to assess the severity of LA. The patients were divided into four groups according to Fazekas scale and the serum 25(OH)D levels of patients in different groups were compared. Correlation analysis and multivariate Logistic regression analysis were used to study the relationship between serum 25(OH)D level and the severity of LA. Results · With the increase of the severity of LA, the serum 25(OH)D levels showed a downward trend, and the difference was statistically significant (P0.000). Correlation analysis showed that serum 25(OH)D levels were negatively correlated with the severity of LA (r-0.534, P0.000). Multivariate Logistic regression analysis showed that the risk factors for LA were increased age (OR1.108, 95% CI 1.054–1.165, P0.000), hypertension (OR2.894, 95% CI 1.060–7.904, P0.038) and decreased 25(OH)D level (OR0.949, 95% CI 0.925–0.974, P0.000). Conclusion · Serum 25(OH)D level is associated with the severity of LA, and is a risk factor for LA.