Abstract：Objective evaluation of left ventricular global systolic function in patients with obstructive sleep apnea syndrome(OSAS) with using three dimensional speckle tracking imaging. And explored the relationship between severity of sleep apnea and left ventricular strain.Methods 41 patients diagnosed with OSAS were selected,divided into mild group 10 cases,moderate group11 cases and severe group 20 cases. Another 20 cases as control group. The measurement of ventricular septal thickness,left ventricular posterior wall thickness, left ventricular mass index, left ventricular ejection fraction and other indexes were measured by routine echocardiography, Left ventricular systolic peak strain in different directions including Global longitudinal peak systolic strain (GLS),Global peak radial systolic strain(GRS), Global circumferential peak systolic strain(GCS)and Global area peak systolic strain(GAS)were measured by 3D-STI. Compared with the differences between the groups,the correlation between the left ventricular area strain parameters and cardiovascular risk factors was analyzed. Result ① BMI of the severe OSAS group increased compared with the control group, the minimum SaO2 of severe and moderate group was lower than other groups, and there were also differences between the two groups; AHI differences between the groups were statistically significant.（P<0.05）②The thickness of ventricular septum, posterior wall thickness of the left ventricle, E/A in the case group and the control group were different, the severe group E/e’was greater than the other groups, and the severe group LVMI was greater than the control group (P<0.05). ③The case group GLS and GAS is less than the control group, and with the severity of the disease was decreasing trend. GRS is less than moderate group, GCS is less than the other groups (P<0.05) ④GAS was positively correlated with AHI and BMI, and negatively correlated with the minimum SaO2.Conclusion 1.The left ventricular function of patients diagnosed as OSAS had already impaired even when the LVEF were still normal, and the level of severity of impairment and OSAS was positively related to each other. 2.The damage of left ventricular area strain was related to AHI, BMI and minimum SaO2.