【Abstract】 Objective To assess whether central venous oxygen saturation (ScvO2) monitoring during spontaneous breathing trial (SBT) could reduce the reintubation rate in difficulttowean patients. Methods All the difficulttowean patients monitored in the intensive care unit from October 16, 2015 to July17, 2016 were taken for the study group. Retrospective analysis of the reintubation rate of difficulttowean patients with different levels of center venous oxygen saturation decreased (ΔScvO2%) during SBT. The gender, age, height, weight, Acute Physiology and Chr onic Health (APACHEⅡ) score, and hemoglobin concentration were cllected. All the patients were divided into high ΔScvO2% group (ΔScvO2%＞4.5%) and low ΔScvO2% group (ΔScvO2%≤45%), and then the reintubation rate were compared between the two groups. The respiratory rate, heart rate, blood pressure, central venous pressure (CVP) and blood gas parameters (pH, PaCO2, PaO2, SaO2, LAC, PcvCO2, PcvO2,ScvO2 ), cardiac output (CO), and cardiac index (CI), ejection fraction of left ventricular (EF) before and after SBT were compared. The increase ratio of CO (ΔCO%), oxygen delivery (ΔDO2%) and the increase of oxygen delivery value (ΔDO2) was calculated and compared. Results All the 25 patients were tracheal extubated after a successful SBT. The reintubation rate in low ΔScvO2% group (1/22) is lower than the high ΔScvO2% group(2/3), P＜005. Conclusion During SBT in difficulttowean patients, patients with ScvO2 reduction≤4.5% may have low rate of reintubation.