Objective：To evaluate the correlation between serum 25-hydroxy vitamin D（25（OH）D） level and carotid artery intimal-medial thickness（IMT）in type 2 diabetic（T2DM） patients. Methods：Totally 132 T2DM patients were divided into four quartile groups（Q1-Q4） according to the level of serum 25（OH）D and were divided into normal group and atherosclerotic group according to their IMT. Their blood pressure，body weight，body height，and biochemical indexes were measured. Their serum 25（OH） D level was mea－sured by ECL. Their carotid IMT，peak systolic velocity，（PSV），end diastolic velocity（EDV） were measured by ultrasongraphy. Results：Carotid IMT in Q1 group was significantly higher than that in Q3 group（P=0.027）. Carotid IMT in Q1 and Q2 groups were signifi－cantly higher than that in Q4 group（P=0.000；P=0.002）. Prevalence of carotid atherosclerotic plaque in Q1 group was significantly higher than that in Q2，Q3 and Q4 groups（P=0.004；P=0.002；P=0.000）. The carotid PSV was significantly lower in Q1 group than that in Q3 group（P=0.031）. Similarly，the carotid EDV was significantly lower in Q1 group than that in Q2，Q3 and Q4 groups（P=0.003；P=0.002；P=0.038）.The serum 25（OH）D concentration was significantly lower in atherosclerotic group than that in normal group（P=0.000）. Pearson correlation analysis showed that carotid IMT was negatively related with the 25（OH）D（r=-0.348，P=0.000）. Multivari－ate regression analysis revealed that 25（OH）D concentration was an independent predictor of carotid IMT in this cohort（B=-0.012，P=0.000）. Conclusion：Serum 25（OH）D concentration is nega－tively correlated with carotid IMT and low 25（OH）D concentra－tion may be a risk factor for carotid atherosclerosis in T2DM pa－tients.