Objective：To investigate the impact of obesity on left ventricular mechanical contraction synchrony parameters in patients with normal myocardial perfusion imaging（MPI）. Methods：A retrospective analysis was conducted on patients who underwent cadmium zinc telluride single photon emission computed tomography（CZT SPECT）MPI at the First Affiliated Hospital of Nanjing Medical University from January 2023 to August 2024. A total of 133 patients with both normal MPI results and normal left ventricular ejection fraction（LVEF）were selected. They were divided into three groups based on body mass index（BMI）：normal group（18.5 kg/m² ≤ BMI＜24.0 kg/m² ，n=40），overweight group（24.0 kg/m² ≤BMI＜28.0 kg/m² ，n=45），and obese group（BMI≥28.0 kg/m² ，n=48）. The differences in left ventricular function parameters such as phase histogram bandwidth（PBW），phase standard deviation（PSD），end - diastolic volume（EDV），end-systolic volume（ESV），and LVEF among the three groups were compared. The relationship between BMI and these parameters was analyzed. Results：Both overweight and obese groups showed significantly higher PBW（22.00 ± 4.24）vs. （17.10±3.20），P ＜ 0.001；（26.13±5.74）vs（. 17.10±3.20），P ＜ 0.001）and PSD values（5.04±1.05）vs.（3.74±0.68），P ＜ 0.001；（6.34± 1.43）vs.（3.74±0.68），P ＜ 0.001）compared with the normal group. The obese group demonstrated significantly greater PBW（26.13± 5.74）vs.（22.00±4.24），P ＜ 0.001）and PSD（6.34±1.43）vs.（5.04±1.05），P ＜ 0.001）than the overweight group. PBW（r=0.446，P ＜0.001）and PSD（r=0.477，P ＜ 0.001）showed significant positive correlations with BMI in overweight and obese patients. Conclusion： Obese patients are more likely to develop left ventricular mechanical dyssynchrony（LVMD），and the novel CZT SPECT phase analysis technique can effectively evaluate left ventricular mechanical synchrony in obese patients at an early stage，providing important clinical guidance for early detection and intervention of LVMD to reduce cardiovascular events in this population.