Abstract: Objective To study the relationship between plasma homocysteine(Hcy), serum 25-hydroxyvitamin D₃(25-(OH)D₃)levels and carotid intima-media thickness(CIMT)in young diabetic patients. Methods A total of 107 young diabetic patients were selected as research objects. CIMT was measured by neck vessels ultrasound, and these patients were divided into severe thickening group(n=29), mild thickening group(n=33)and thickening-free group(n=45)according to the values of CIMT, and 107 healthy volunteers in the same period with physical examinations were selected as control group. The plasma Hcy and serum 25-(OH)D₃ levels were detected, and their differences in differed groups and their relationship with CIMT were observed. Results Severe thickening group, mild thickening group and thickening-free group had significantly higher plasma Hcy levels that the control group(P<0.05), and significantly lower serum 25-(OH)D₃ levels than the control group(P<0.05). The subjects' CIMT had a positive correlation with plasma Hcy level(r=0.463, P<0.001), and a negative correlation with serum 25-(OH)D₃ level(r=-0.339, P<0.001). Logistic regression analysis showed that high level of plasma Hcy and lower level of serum 25-(OH)D₃ were both independent risk factors of CIMT thickening for young patients with diabetes(P<0.001). Conclusion The levels of plasma Hcy and serum 25-(OH)D₃ in young diabetic patients can reflect the condition of CIMT to a certain extent, and can be used as important indicators to evaluate the risk of macro-vascular disease in young diabetic patients. Meanwhile, they provide guidance - for the diagnosis and treatment of these patients.