Aim To investigate the changes of carotid intima media thickness (CIMT) in patients with sleep apnea hypopnea syndrome (OSAHS), and to explore the correlation between CIMT and 25(OH)D levels in OSAHS patients.Methods The portable sleep monitor (PM) was used to monitor the sleep condition of the people reference for the health examination. According to sleep apnea hypopnea index (AHI), they were divided into control group, mild OSAHS group, moderate OSAHS group and severe OSAHS group. CIMT and the levels of 25(OH)D in the four groups were compared to analyze the correlation between CIMT and 25(OH)D. Results CIMT in severe OSAHS group was higher than that in control group and mild OSAHS group ((0.88±0.15) mm vs (0.75±0.14) mm and (0.76±0.14) mm, all P＜0.05), the difference was statistically significant. The level of 25(OH)D in the moderate and severe OSAHS group was lower than that in the control group ((19.06±6.04) μg/L and (17.67±4.73) μg/L vs (22.78±7.40) μg/L, all P＜0.05), the difference was statistically significant. After adjusting the influences of various hybrid factors, multiple linear regression analysis demonstrated that CIMT in OSAHS patients was positively correlated with AHI (P＝0.006) and negatively correlated with 25(OH)D (P＝0.024). Conclusion CIMT in OSAHS patients increases with the increase of severity. 25(OH)D deficiency may be a risk factor for carotid intimal thickening in OSAHS patients.