This study is an open-label Phase Ib clinical study with the primary objective of evaluating the safety and tolerability of multiple subcutaneous injections of SHR-2004 injection in patients with atrial fibrillation, and the secondary objective is to evaluate its pharmacokinetic (PK), pharmacodynamic (PD) and immunogenicity characteristics.

Inclusion Criteria:

1. Understand the study procedures and methods, voluntarily participate in this trial, and sign the informed consent form in writing;
2. Male or female ≥ 40 years and < 80 years old；
3. History of atrial fibrillation or atrial flutter, or newly diagnosed atrial fibrillation or atrial flutter during the screening period, as documented by Holter ECG or 12-lead ECG at the time of screening or within 12 months prior to screening.

Exclusion Criteria:

1. Patients with a mechanical heart valve;
2. Rheumatic mitral stenosis or moderate to severe non-rheumatic mitral stenosis;
3. Atrial fibrillation or atrial flutter is caused by reversible causes, or successful ablation has been converted to sinus rhythm, or cardioversion or ablation surgery is planned during the study;
4. Concomitant poorly controlled hypertension (systolic blood pressure ≥160 mmHg and/or diastolic blood pressure ≥100mmHg) at screening;
5. Those who are allergic to the trial drug or any component of the trial drug;
6. Unstable or severe liver, renal, cardiovascular, psychiatric, neurological, endocrine, hematological and other diseases at the time of screening, and the investigator judges that it is not suitable to participate in the study;
7. Females who are pregnant or lactating.