Objective：To establish and validate a nomogram prediction model for the activated clotting time（ACT）measured 30 minutes after the first dose of heparin（30 min-ACT）in patients with atrial fibrillation undergoing radiofrequency ablation. Methods： From January 2020 to December 2022，1 090 patients with non-valvular atrial fibrillation who underwent catheter radiofrequency ablationinthe catheter room of the Department of Cardiology，the First Affiliated Hospital of Nanjing Medical University were included. These patients were randomly divided into a training set and a testing set in a 3∶1 ratio. Kruskal-Wallis and Chi-square tests were used to compare the baseline characteristics of the two groups. LASSO regression and univariate and multivariate linear regression analyses were conductedto identify factors influencing 30 min-ACT. Based on these findings，a prediction model for 30 min-ACT with the first dose of heparin during radiofrequency ablation in patients with atrial fibrillation was established and evaluated. Results：Multivariate analysis suggested that stroke history，warfarin use，platelet count，prothrombin time（PT），baseline ACT，baseline ACT² ，and first dose of heparin were independent predictors of first dose of heparin ACT during radiofrequency cardiac ablation in patients with atrial fibrillation. The resulting nomogram prediction model showed a certain level of accuracy（training set 65.9%，testing set 74.6%）and higher sensitivity（training set 77.4%，testing set 83.0%）. Conclusion：The 30 min -ACT nomogram model，based on stroke history， warfarin ues，platelet count，PT，baseline ACT，baseline ACT² ，and first dose of heparin，can predict the anticoagulant effect of the first dose of heparin in atrial fibrillation patients，providing valuable clinical guidance.