Objective: To compare the value of 25-hydroxyvitamin D3 (25-(OH)D3) with other clinical parameters in the prediction and diagnosis of eosinophilic chronic rhinosinusitis with nasal polyps (ECRSwNP). Methods: Eligible chronic rhinosinusitis with nasal polyps (CRSwNP) patients and healthy subjects in the Affiliated Hospital of Guizhou Medical University from January to April of 2021 were included for this study. The age, gender, past history and other basic characteristics of all subjects were recorded. The CRSwNP patients were classified into ECRSwNP and non-eosinophilic chronic rhinosinusitis with nasal polyps (nECRSwNP) endotypes by the percentage of tissue eosinophils. Serum 25-(OH)D3 levels measurements were performed in all subjects. Paranasal sinus CT scans, blood eosinophil counts, and determination of total immunoglobulin E (total IgE), Th1/Th2 plasma cytokines and nasal nitric oxide (nNO) levels were performed before surgery. Logistic regression analysis was used to evaluate the related factors of ECRSwNP. Receiver operating characteristic (ROC) curves was used to evaluate the predictive potential of the clinical parameters. Results: One hundred and twenty-seven CRSwNP patients and 40 healthy subjects were recruited, including 74 males and 93 females of the patients, with the age of (38.73±13.05) years. In patients with ECRSwNP, serum 25-(OH)D3 levels were significantly lower than those in nECRSwNP patients ((26.14±4.58) ng/ml vs (35.71±7.86) ng/ml, t=-8.564, P<0.01). The prevalence of asthma, prevalence of allergic rhinitis, peripheral blood eosinophil counts, total IgE levels, nNO levels and CT scores ratio for ethmoid sinus and maxillary sinus (E/M ratio) of ECRSwNP patients were significantly higher than those in nECRSwNP patients (all P<0.05). However, there was no significant difference in Th1/Th2 cytokines levels between the histological types of CRSwNP (all P>0.05). Among the predictive indicators, 25-(OH)D3 had the highest predictive value, with ROC area under curve (AUC) value of 0.882. The best cut-off point of 28.5 ng/ml for 25-(OH)D3 demonstrated a sensitivity of 0.871 and a specificity of 0.762 for ECRSwNP. Conclusion: Measurement of serum 25-(OH)D3 level may be used as an effective method to distinguish between ECRSwNP and nECRSwNP.