Objective：To evaluate the effect of obesity on left atrial function in patients with essential hypertension by using a combined approach of two-dimensional speckle tracking imaging（2D-STI）and real -time three-dimensional echocardiography（RT-3DE）. Methods：A total of 132 patients diagnosed with essential hypertension and 114 controls with normal blood pressure were enrolled from Jiangning Hospital Affiliated to Nanjing Medical University from April 2022 to July 2023. According to the body mass index（BMI），they were stratified into six subgroups. Left atrial longitudinal strain and mechanical function indices were obtained using the combined 2D-STI and RT-3DE techniques to compare differences in left atrial function among the groups. Results：Compared to the healthy control group with the same BMI category，the hypertension group showed a decrease in left atrial reservoir strain（LASr） and left atrial conduit strain（LAScd）（P < 0.05）；As BMI increased，LASr，LAScd，total left atrial ejection fraction（LAEFt），passive left atrial positive ejection fraction（LAEFp），and active left atrial ejection fraction（LAEFa）decreased in hypertension patients（P < 0.05），while left atrial contractile strain（LASct）showed no significant difference（P > 0.05）. Multivariate linear regression analysis revealed that BMI was independently negatively correlated with LASr，LAScd，LAEFt，LAEFp and LAEFa in the hypertension group， respectively（P < 0.05），while systolic blood pressure showed no significant correlation with left atrial function in hypertensive patients （P > 0.05）. Conclusion：Hypertension can lead to the impairment of left atrial function and with an increase in BMI，especially when combined with obesity，the damage to left atrial function may be further exacerbated to a certain extent.