Aim To investigate the relationship between circadian rhythm of blood pressure and arterial stiffness. Methods We collected and analyzed ambulatory and clinical data in inpatients of a comprehensive department during 2004-2008 in the Affiliated Hospital of Dali University. Results In 242 inpatients,before and after adjustment of age,sex,antihypertensive treatment,24 h pulse rate and mean arterial blood pressure,compared with dippers(n=85),non-dippers(n=103),reverse dippers(n=42) and extreme dippers(n=12) had a significantly higher ambulatory arterial stiffness index and 24 h pulse pressure.There was no significant difference in age,plasma glucose,uric acid,total cholesterol and triglyceride among four groups(P>0.05). Conclusion Abnormal circadian rhythm of blood pressure was associated with arterial stiffness.