Objective To investigate the predictive value of lactate (Lac) and complex model for the occurrence of prolonging mechanical ventilation (PMV) after off-pump coronary bypass grafting (OPCABG) based on dose-response analysis and decision curve analysis. Methods A retrospective analysis was conducted on 683 patients who underwent OPCABG from January to December 2019 in the Department of Cardiovascular Surgery of the General Hospital of the Northern Theater Command. These patients were divided into PMV group (n=107) and non-PMV group (n=576) based on whether duration of prolonged mechanical ventilation was longer than 24 h. The arterial blood lactate at 0 h and 6 h after admission to the ICU of cardiovascular surgery,baseline data and other clinical indicators of the patients were recorded. Preoperative, intraoperative and postoperative risk factors affecting PMV time were analyzed by univariate analysis, and a prediction model was established by indicators selected by logistic regression. Restricted cubic spline model, decision curve analysis (DCA) and receiver operating characteristic (ROC) curve were used to evaluate the predictive value of arterial blood lactate and complex model. Results There were no significant differences between PMV group and non-PMV group in gender, age, BMI, NYHA cardiac function classification, history of myocardial infarction, history of PCI, smoking history, hypertension, diabetes, hypercholesterolemia, >50% stenosis with of 3 coronary artery branches and left aortic stenosis >50%, number of blood vessel bridge, arterial blood lactate at 0 h after admission to ICU,preoperative serum creatinine, hemoglobin after operation, preoperative total bilirubin, preoperative direct bilirubin (P>0.05). There were statistically significant differences in the use of IABP, left ventricular ejection fraction (LVEF), pulmonary arterial pressure,preoperative red blood cell distribution width (RDW), arterial blood lactate at 6 h after admission to ICU, preoperative hemoglobin,preoperative hypersensitive CRP (hs-CRP), postoperative hs-CRP, preoperative troponin T (TNT) and preoperative amino-terminal pro-brain natriuretic peptide (NT-proBNP) (P<0.05). Multivariate logistic regression analysis showed that preoperative RDW, arterial blood lactate 6 h after admission to ICU, pulmonary arterial pressure, preoperative NT-proBNP were risk predictors of PMV, and use of IABP was protective predictor of PMV (P<0.05), OR of five factors were 1.242 (95%CI 1.001-1.539), 1.370 (95%CI 1.171-1.604), 1.043 (95%CI 1.002-1.087), 2.065 (95%CI 1.333-3.200), 0.146 (95%CI 0.071-0.301), respectively (P<0.05). The area under the receiver operating characteristic curve of arterial blood lactate 6 h after admission to ICU and complex model were 0.582 (95%CI 0.518-0.646), 0.727 (95%CI 0.674-0.781), respectively. Intensity of association between Lac 6 h and the development of PMV exhibited a non-linear dose response relationship (P<0.01). Decision curve analysis showed that compared with Lac 6 h, the complex model had a higher net benefit when the threshold probability was between 0.05 and 0.75. Conclusions Compared with Lac 6 h, complex model has a higher predictive value for the occurrence of PMV after OPCABG.