Background:We wanted to demonstrate whether the initial platelet-to-albumin ratio (PAR) had predictive value for cardiac surgeryassociated acute kidney injury (CSA-AKI) and prognosis of critical care patients. Methods: This is an observational and multi-center study from the MIMIC-IV database, the eICU-CRD database as well as CS patients at our institution. Logistic regression and Cox regression analyses were applied to determine the predictive value for CSA-AKI and in-hospital mortality. LASSO and SVM-RFE models were then employed to discover the coincident variables connected with CSA-AKI. The main objective of this research was the incidence of CSA-AKI, whereas the secondary endpoint was in-hospital death. Results: The higher PAR value (≥4.67) had a higher risk of CSA-AKI (adjusted OR = 4.02, 95% CI 3.41-4.75, P < 0.001) and in-hospital mortality (HR = 2.41 95% CI 1.44-4.03, P = 0.001) after adjusted for other confounding factors including patients with or without chronic kidney disease. The proposed nomogram based on PAR and others clinical factors selected by LASSO and SVM-RFE models for CSA-AKI had the C-index 0.821 (95% CI 0.807-0.834), 0.808 (95% CI 0.787-0.829), 0.745 (95% CI 0.728-0.762), and 0.826 (95% CI 0.753-0.899) in these cohorts, respectively. The nomogram exhibited both remarkable calibration capacity and therapeutic helpfulness in all groups. Conclusion: PAR is a relative excellent measure for the event AKI and prognosis of ICU patients who undergone CS. The suggested nomogram based on PAR resulted in an accurate prediction for the detection of critical care patients with CSA-AKI.