Objective: To analyze the value of serum creatinine (SCR), cystatin C (CysC) and homocysteine (Hcy) levels in predicting the occurrence of contrast-induced nephropathy (CIN) in acute coronary syndrome (ACS) after Percutaneous coronary intervention (PCI). Methods: A total of 87 ACS patients admitted to our hospital for PCI from January 2018 to March 2020 were collected continuously. According to whether CIN occurred after the surgery, they were divided into a CIN group (with CIN) and a non-CIN group (without CIN). Serum Scr, CysC and Hcy levels were compared between the 2 groups, and risk factors related to CIN were analyzed by multivariate logistic regression. In addition, ROC curve was drawn to analyze the predictive value of serum CysC and Hcy to CIN. Results: A total of 87 patients with ACS were relieved after PCI, but 30 cases developed CIN after PCI, the incidence rate was 34.5%. Smoking, hypertension, and diabetes in the CIN group were significantly higher than those in the non-CIN group (all P<0.05). The serum levels of SCR, CysC and Hcy in the CIN group were significantly higher than those before the operation (all P<0.05), and higher than those in the non-CIN group in the same period (all P<0.05). There was no significant difference in serum SCR, CysC and Hcy between the 2 groups before the operation (P>0.05). Logistic regression analysis showed that serum CysC and Hcy were independent risk factors for CIN. ROC curve showed that the value of serum CysC and Hcy in predicting the occurrence of CIN after 48 h was relatively high, and the optimal critical value of CysC was 1.4 mg/L, AUC was 0.764 (95%CI: 0.664~0.863), while Hcy was 10.2 mol/L, and AUC was 0.813 (95%CI: 0.720~0.907). Conclusion: Serum CysC and Hcy are independent influencing factors for CIN complications in ACS patients after PCI, and these indicators are significantly abnormal in these patients. Detection of these indicators 48 h after the surgery can effectively predict the occurrence of CIN.