Objective To observe the effects of valsartan/ hydrochlorothiazide and valsartan on left ventricular thickness and the left ventricular diastolic function in patients with essential hypertension and left ventricular hypertrophy and impaired left ventricular diastolic function. Methods 56 patients of essential hypertension with left ventricular hypertrophy and impaired left ventricular diastolic function were randomized into two randomized double-blind groups, valsartan/hydrochlorothiazide (HCTZ) 80/12.5 mg o.d were gave to A group and valsartan 80 mg o.d were gave to B group. The dosage would be doubled in patients whose SDBP ≥ 12 kPa or SSBP ≥ 18.7 kPa after 4 weeks. Treatment lasted for 6 months. Result At the end of 6 months, valsartan/ hydrochlorothiazide and valsartan significantly reduced BP from baseline (Plt;0.01), there was significant difference in reducing BP between the two groups (Plt;0.05). Indexes of left ventricular diastolic function (IVST, LVPWT, LVMI) significantly decreased (Plt;0.01). LVEF increased significantly (Plt;0.01). There was significant difference in IVST, LVPWT, LVMI and LVEF between two groups (Plt;0.05). Conclusion Valsartan/ hydrochlorothiazide (HCTZ) can not only decrease blood pressure effectively, but also can significantly improve left ventricular hypertrophy and left ventricular diastolic function.