Objective To explore the risk factors for hyponatremia in hospitalized Acute exacerbation of chronic obstructive pulmonary disease (AECOPD) patients. Methods In this retrospective cross-sectional study, from January 2019 to June 2020, 327 hospitalized AECOPD patients were enrolled. 165 AECOPD with normal natrium (NN-AECOPD), and 50 AECOPD with hyponatremia (LN-AECOPD) were included. Demographic data, underlying diseases, lung function, blood routine, procalcitonin (PCT), C-reaction protein (CRP), and arterial blood gas (ABG) data were recorded. Binary logistics regression was performed to explore the independent risk factors for hyponatremia in AECOPD patients. Results The significant differences in 6 variables, including the rates of pleural effusion, community acquired pneumonia (CAP), and type 2 diabetes (T2DM), lymphocytes%, and serum magnesium (Mg2+), were included in binary logistics regression. Subsequently, we identified that the rates of CAP (R=5.109, P<0.001) was independently associated with hyponatremia in hospitalized AECOPD patients.Conclusion The results indicate that CAP is an independent risk factor for hyponatremia in AECOPD patients. Then, hyponatremia is more common in AECOPD combined with CAP. Additionally, CAP should be seriously considered in AECOPD patients with hyponatremia