Objective To explore the relationship between EOS infiltration and clinical characteristics and IL-17 expression changes in patients with chronic sinusitis with nasal polyps. Methods Selected 100 patients with chronic sinusitis with nasal polyps admitted to our hospital from January 2020 to October 2022, grouped patients according to whether patients had EOS infiltration, control group (n=55, without EOS infiltration), observation group (n=45, EOS infiltration), all patients underwent nasal endoscopy, and nasal polyp tissue was retained for use. Interleukin-17 (IL-17) level in nasal polyps tissue and peripheral venous serum; performed nasal endoscopy and CT, evaluated the extent and extent by Lund-Kennedey score and Lund-Mackey score; the clinical data was collected, comparing the factors that might affect the EOS infiltration, exploring the correlation between EOS infiltration and IL-17 in the lesion tissue and serum. Results Age, sex ratio, disease duration, neutrophil percentage, percentage of lymphocytes and lesion classification of the two groups were compared with no significant difference (P> 0.05). The Lund-Kennedey score of polyps, edema and nasal leak was higher than the control group, but the difference was not significant (P> 0.05). The CT and Lund-Mackey scores in the observation group were much higher in the ethmoid sinus, nasal sinus complex, sphenoidal sinus and sphenoid fossa site than the control group, but the maxillary sinus score was lower than that in the control group, significant (P <0.05) and sinus and frontal sinus scores in the anterior group (P> 0.05). Compared with the control group, IL-17 levels increased significantly in the observation group (P <0.05). After Pearson correlation analysis, there was positive correlation between IL-17 level of serum and nasal polyp tissue,recess and sinus lesions and EOS infiltration, statistically significant (| r |> 0.5, P> 0.05), maxillary sinus lesions were negatively associated with EOS infiltration, statistically significant (| r |> 0.5, P> 0.05), and nasal sinus complex, ethmoid and nasal leak in posterior group had low correlation with EOS infiltration. Conclusion During EOS infiltration in chronic sinusitis with nasal polyps, IL-17 levels in lesion tissues and serum were significantly increased; IL-17 levels, sphenoid recess and sphenoid sinus lesions were positively associated with EOS infiltration, and maxillary sinus lesions.