Objective：To evaluate ventricular segments motion on AAI mode and DDD mode with optimal atrioventricular interval by the quantitative tissue velocity imaging（QTVI）， and to investigate whether AAI pacing mode was superior ｔｏ the DDD pacing mode with optimal atrioventricular interval in sick sinus syndrome（SSS） patients withⅠdegree atrioventricular block（I°AVB）. Methods：Twenty four patients with implanted DDD pacemakers for SSS with I°AVB（PR interval ＞ 2０0 ms and < 260 ms） were studied at four-chamber view, two-chamber view and apical longitudinal view using QTVI. The regional parameters, including peak sustained velocity（Vs）, peak early diastolic velocity（Ve）, peak late diastolic velocity（Va） and peak systolic displacement（D） of the basal and middle segments in left ventricle（anterior septal, anterior, lateral, posterior, inferior and septal wall） and in the free wall of right ventricle were measured. Results：There were significant differences in the parameters（Vs, Ve） of most basal segments between AAI group and DDD group（P ＜ 0.05）. There were no significant differences in other parameters between both modes（P ＞ 0.05）. Conclusion：① In AAI pacing mode, ventricular systolic and diastolic function are superior to DDD pacing mode with optimal atrioventricular interval in patients with SSS, which intrinsic AV conduction are moderately prolonged; ②The change of ventricle segments motion can be early evaluated by QTVI in AAI and DDD mode, and it is useful to determine the optimal pacing mode in SSS patients withⅠ° AVB.