Objective To investigate the effect of plasma homocysteine(Hcy) on the changes of left ventricular geometry in patients with obstructive sleep apnea syndrome (OSAS). Methods A total of 192 patients with OSAS diagnosed with apnea index (AHI)≥5times/h by polysomnography (PSG) were selected. Blood pressure, blood glucose, blood lipids, and plasma homocysteine levels were measured the next morning. For echocardiography, 30 healthy people whose gender, age match, blood glucose, blood lipids, chest radiograph, electrocardiogram and PSG were normal were selected as the control group. According to the left ventricular mass index (LVMI) and relative wall thickness (RWT), OSAS patients are divided into four groups according to the geometric configuration of the left ventricle: normal configuration group (NG), concentric remodeling group (CR), and concentric hypertrophy Group (CH), eccentric hypertrophy group (EH). The difference of plasma Hcy levels between the control group and the OSAS four groups was compared, and the single-factor correlation analysis between plasma Hcy and other parameters was performed, and the multivariate stepwise regression analysis was further performed. Results ① Compared with the control group, the plasma Hcy levels of the CR, CH, and EH groups increased, and the difference was statistically significant (P<0.05); compared with the NG and CR groups, the plasma Hcy levels of the CH and EH groups increased High, the difference was statistically significant (P<0.05); Compared with the EH group, the plasma Hcy level in the CH group increased, and the difference was not statistically significant (P>0.05); ② Univariate correlation analysis of plasma Hcy and BMI, SBP , Abdominal circumference, AHI, blood glucose, LVMI, abnormal left ventricular geometric configuration are positively correlated, and are negatively correlated with Em/Am, LVEF, and are correlated with gender, age, DBP, neck circumference, hip circumference, T90, MSaO2, LSaO2, RWT No correlation; ③Further analysis of multivariate stepwise linear regression showed that plasma Hcy was independently related to AHI, LVMI, and abnormal left ventricular geometry. Conclusion The expression levels of plasma Hcy in patients with different left ventricular geometric configurations of OSAS are different. The level of plasma Hcy is one of the main influencing factors of changes in left ventricular geometric configuration (CH, EH) in patients with OSAS.