Abstract: Objective To investigate the impairment of heart function and its mechanism in Diabetes Melliuts. Methods By using Doppler echocardiography, the cardiac function, clinical and lab findings of 60 Diabetes Mellitus patients were collected and researched. The correlation among echo data and those clinical and lab findings was analysed. Results It was demonstrated that left ventricular ejection function (LVEF) in DM patients was decreased,but LVEF remained in the normal range. E/A,E1/A1 and Ta/Td of the transmitral Doppler velocity curve were decreased. These parameters were negatively correlated to age and blood glucose level. Conclusion Impaired left ventricular (LV) diastolic function was found in DM patients. The significant increase of blood glucose was the main risk factor for the aggravated impairment of LV relaxation.