The objective of this study was to investigate the predictive value of perioperative lactate clearance rate (LCR) for 30-day composite adverse outcomes in patients undergoing off-pump coronary artery bypass grafting (OPCAB). A total of 480 patients who underwent elective OPCAB between June 2024 and June 2026 were included, of whom 80 had composite adverse outcomes and 400 had favorable outcomes. Perioperative clinical baseline data, blood lactate levels, and laboratory parameters were collected. Factors influencing 30-day composite adverse outcomes after OPCAB were analyzed, and receiver operating characteristic (ROC) analysis was performed to evaluate the predictive performance of lactate clearance rate for short-term postoperative adverse outcomes. Univariate analysis showed that age, history of preoperative hypertension, history of diabetes mellitus, proportion of patients with preoperative NYHA class III-IV, operative duration, intraoperative blood loss, perioperative blood glucose, cTnI, NT-proBNP, CRP, and D-dimer levels were higher in the adverse outcome group than in the favorable outcome group, whereas oxygenation index, eGFR, PLT, and ALB levels and lactate clearance rates at postoperative T6, T12, and T24 were lower than those in the favorable outcome group (P<0.05). Multivariate Logistic regression analysis showed that preoperative NYHA class III-IV, high perioperative NT-proBNP, low ALB, decreased lactate clearance rates at postoperative T6, T12, and T24, and increased EuroSCORE II score were independent risk factors for 30-day composite adverse outcomes after OPCAB (P<0.05). ROC curve analysis showed that postoperative T12 lactate clearance rate had the best predictive value, with an area under the curve (AUC) of 0.887. After correction by 1,000-bootstrap internal validation, the AUC was 0.861, with no significant attenuation in predictive performance. The AUC of T12 lactate clearance rate was higher than that of the EuroSCORE II score (AUC=0.742, P<0.001). DCA results showed that within the risk threshold range of 0.05-0.85, the clinical net benefit of the T12 lactate clearance rate model was superior to that of the EuroSCORE II score alone. Lactate clearance rates at postoperative T6, T12, and T24 were independent factors influencing short-term postoperative adverse outcomes. Postoperative 12-h lactate clearance rate retained excellent predictive performance after internal validation and demonstrated incremental predictive value compared with the traditional EuroSCORE II score, and it can be used as a predictive indicator for the early clinical identification of high-risk patients after OPCAB.