This study is a prospective, multi-center, randomized controlled trial. The subjects are patients scheduled to undergo a combined procedure of atrial fibrillation (AF) ablation and left atrial appendage (LAA) occlusion. After signing the informed consent form, the subjects will be randomly assigned to either the cardiac Computed Tomography (CT) group or the Digital Subtraction Angiography (DSA) group. The operator will select the appropriate LAA occluder size for implantation based on different measurement methods. All subjects will undergo clinical follow-up before discharge and at 3 months postoperatively, as well as telephone follow-up 1-5 years after the surgery.

Inclusion Criteria:

1. Age ≥ 18 years;
2. Patients with non-valvular atrial fibrillation scheduled to undergo atrial fibrillation ablation and percutaneous left atrial appendage occlusion;
3. Able to understand the purpose of the trial, willing to participate in the study, and the subject or their legal representative has signed the informed consent form, and is willing to complete the follow-up according to the protocol requirements.

Exclusion Criteria:

1. Allergy to contrast agents or other conditions that preclude cardiac CT or DSA imaging;
2. Absence of clear images for measuring the diameter of the LAA in all layers of the CT scan;
3. Imaging indicates the presence of thrombus in the left atrium or LAA;
4. Patients with valvular AF (mechanical valve replacement or moderate to severe mitral stenosis combined with AF);
5. LAA depth < 15 mm, or LAA anchor zone diameter < 10 mm or > 33 mm;
6. Female patients of childbearing age planning to become pregnant during the follow-up period required by this study;
7. Currently participating in another clinical trial of drugs or medical devices and has not yet completed the primary endpoints of that study, which may confound the results of this study or affect the participant's compliance with the follow-up;
8. Other conditions that the investigator deems make the participant unsuitable for this study.