Objective To investigate the value and clinical significance of multislice spiral computed tomography (MSCT) in the diagnosis of atrial fibrillation (AF) in patients with coronary heart disease, and to provide a reference for making an early confirmed diagnosis and formulating treatment regimens. Methods A total of 62 patients with coronary heart disease and AF who were treated in our hospital from January 2020 to October 2022 were enrolled as study group, and 50 coronary heart disease patients without AF during the same period of time were enrolled as control group. All patients underwent MSCT after admission. MSCT parameters (epicardial adipose tissue [EAT] volume, left atrial appendage ejection fraction [LAAEF], left atrial appendage ejection volume (LAAEV), and Left atrial ejection force (LAEF)] were compared between the two groups and between the patients with different types of AF to analyze the association between MSCT parameters and AF and the diagnostic value of MSCT parameters. Results Compared with the control group, the study group had a significantly higher EAT volume and significantly lower LAAEF and LAEF on admission (P<0.05), and compared with the patients with persistent AF, the patients with paroxysmal AF had a significantly lower EAT volume and significantly higher LAAEF and LAEF on admission (P<0.05). The Pearson correlation analysis showed that EAT volume on admission was positively correlated with the comorbidity with AF and the type of AF, while LAAEF and LAEF were negatively correlated with the comorbidity with AF and the type of AF (P<0.05). EAT volume, LAAEF, and LAEF on admission had an area under the ROC curve (AUC) of 0.856, 0.832, and 0.795, respectively, in the diagnosis of coronary heart disease comorbid with AF, while the combination of these three indices had an AUC of 0.932, suggesting that the combination of the indices had a better diagnostic value than each index alone. Conclusion EAT and LAAEF measured by MSCT are closely associated with the comorbidity with AF and the type of AF in patients with coronary heart disease, and they can be used for early diagnosis in clinical practice, so as to formulate targeted intervention regimens and improve prognosis.