Objective To investigate the value of remnant lipoprotein cholesterol（RLP-C）and homocysteine（Hcy）in predicting new-onset atrial fibrillation（AF） in elderly patients with acute myocardial infarction（AMI）. Methods A total of 449 elderly patients with AMI admitted to the Cardiology Department of Langfang Fourth People’s Hospital from January 2018 to June 2023 were enrolled as the research objects. The patients were divided into AF group (n=90) and non-AF group (n=359) according to the occurrence of new-onset AF during hospitalization. The clinical data of the two groups were collected. Logistic regression was used to analyze the risk factors of new-onset AF, and receiver operating characteristic (ROC) curve was used to judge the predictive effect of each index on new-onset AF. Results Compared with the non-AF group, the heart rate on admission, RLP-C and Hcy levels in the AF group were increased (P<0.05). There were significant differences in Killip grades between the two groups (P<0.05). Logistic regression analysis showed that heart rate on admission, RLP-C and Hcy were independent risk factors for new-onset AF (P<0.05). ROC curve analysis showed that the AUC of RLP-C, Hcy and their combination in predicting new-onset AF in elderly patients with AMI were 0.761, 0.720 and 0.845, respectively. The AUC of RLP-C and Hcy combined prediction was higher than that of single prediction (Z=3.061, 3.692, P<0.05). Conclusions RLP-C and Hcy are independent predictors of new-onset AF in elderly patients with AMI. The combination of RLP-C and Hcy can further improve the predictive value.