Objective: To establish and verify the prediction model of activated clotting time (ACT) measured 30 minutes after the first dose of heparin in patients with atrial fibrillation during radiofrequency ablation. Methods: A single-center retrospective study design was adopted. From January 2020 to December 2022, 1090 patients with nonvalvular atrial fibrillation were selected for radiofrequency cardiac catheter ablation with the catheter room of the Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University. Patients were randomly divided into the training set and testing set in a 3:1 ratio. Kruskal-Wallis test and Chi-square test were used to compare baseline characteristics of the training set and testing set. LASSO regression, univariate and multivariate linear regression were used to analyze the independent factors influencing 30min-ACT. Based on this, the prediction model of 30min-ACT with the first dose of heparin during radiofrequency ablation in patients with atrial fibrillation was established and its predictive effect was evaluated. Results: Multivariate analysis of results suggested that stroke history, warfarin, platelet count, prothrombin time, basal ACT, basal ACT2, and first dose of heparin were independent predictors of first dose of heparin ACT during radiofrequency cardiac ablation in patients with atrial fibrillation, and the prediction model based on the constructed histogram had a certain accuracy (training set = 65.9%, testing set = 74.6%) and higher sensitivity (training set = 77.4%, testing set = 83%). Conclusion: Based on stroke history, warfarin, platelet count, PT, baseline ACT, baseline ACT2 and first dose of heparin, the nomogram model can predict the anticoagulant effect of the first dose of heparin in atrial fibrillation patients, 30min-ACT, providing valuable clinical guidance.