Objective: To investigate the association between preoperative apolipoprotein B/apolipoprotein A1 ratio (ApoB/ApoA1) and the risk of developing acute kidney injury (AKI) following off pump coronary artery bypass grafting (OPCABG). Methods: A retrospective cohort study was conducted. Clinical data from 107 patients who underwent OPCABG were collected. Patients were divided into an AKI group (n = 34) and a non-AKI group (n = 73) based on postoperative occurrence of AKI defined by KDIGO criteria. Data, including gender, age, comorbidities, preoperative laboratory parameters (ApoB/ApoA1 ratio, albumin, hemoglobin, serum creatinine), and surgical approach, were collected and compared between the two groups. Univariate and multivariate Logistic regression analyses were performed to identify independent risk factors for postoperative AKI. Results: The preoperative ApoB/ApoA1 ratio was higher in the AKI group than in the non-AKI group (P < 0.05). Univariate analysis revealed that body weight and ApoB/ApoA1 ratio were influencing factors for AKI (P < 0.10). Multivariate Logistic regression analysis demonstrated that after adjusting for age, body weight, and preoperative serum creatinine, a higher preoperative ApoB/ApoA1 ratio remained an independent risk factor for AKI following OPCABG (P < 0.05). Conclusion: An elevated preoperative ApoB/ApoA1 ratio is independently associated with an increased risk of AKI after OPCABG. This ratio may serve as a potential biomarker for preoperative assessment of renal injury risk.