Aim To investigate the relationship between ambulatory arterial stiffness index (AASI) and left ventricular diastolic function in patients with essential hypertension. Methods 143 patients who had been diagnosed with essential hypertension were divided into two groups, with or without left ventricular diastolic dysfunction group. At the same time 60 patients with normal blood pressure were enrolled into control group. Uric acid (UA), total cholesterol (TC), low density lipoprotein (LDL), high density lipoprotein (HDL), fasting blood glucose (FBG), homocysteine (Hcy) and high sensitive C reactive protein (hs-CRP) were measured before treatment. The AASI were detected by 24-hour ambulatory blood pressure monitoring. Left ventricular diastolic function was assessed by pulsed Doppler tissue imaging. Subsequently, the relationship was analysed between AASI and left ventricular diastolic function. Results There were no significant differences in sex, age, body mass index (BMI), FBG, TC, HDL among three groups(P＞0.05). The AASI, UA, Hcy, hs-CRP and LDL were significantly higher in left ventricular diastolic dysfunction patients (P＜0.05). The AASI was negatively correlated with E/A (r=－0.697, P＜0.05) and positively correlated with E/Ea(r=0.614, P＜0.05). Conclusion AASI might be a marker of diastolic dysfunction in essential hypertension patients.