Objective To explore the association between QT interval parameters, disease severity, and myocardial injury in elderly patients with liver cirrhosis. Methods 235 elderly patients with liver cirrhosis treated in Beijing You'an Hospital, Capital Medical University from February 2021 to February 2025 were enrolled. They were grouped by Child-Pugh classification (grade A:75, B:89, C:71) and myocardial injury status (injury group:92; non-injury group:143). Generalized additive model (GAM), multivariate Logistic regression, restricted cubic spline (RCS) and generalized linear model were used to analyze relationships and interactions between QT interval parameters, liver function classification and myocardial injury. Results Statistically significant differences were observed in coagulation, liver/kidney function, myocardial enzymes, and QT interval (QT), heart rate-corrected QT interval (QTc), QT dispersion (QTd), T wave peak to end interval (Tp-Te), and cardiac troponint (cTnT) among different liver function grades (P＜0.05). GAM analysis showed QT, QTc, QTd, and Tp-Te positively affected liver function grading (P＜0.05). Multivariate Logistic regression identified liver function grade, QT, QTc, QTd, and Tp-Te as independent factors for myocardial injury (P＜0.05). RCS revealed a positive non-linear dose-response between these QT parameters and myocardial injury (P＜0.001). Myocardial injury proportion increased with higher liver function grades and QT parameters (P＞0.05), with their positive correlation strengthening as liver function grade rose. Conclusion QT, QTc, QTd, and Tp-Te in elderly patients with liver cirrhosis are positively correlated with disease severity and the risk of myocardial injury, which can provide a basis for the early clinical assessment of disease progression and myocardial injury