Objective: To investigate the effect of blood eosinophils on clinical effect of endoscopic sinus surgery for chronic rhinosinusitis with nasal polyps (CRSwNP). Methods: From March 2011 to March 2016, 72 cases with CRSwNP were treated by endoscopic sinus surgery in Department of Otorhinolaryngology Head and Neck Surgery, Peking University People's Hospital. The clinical records were retrospectively reviewed, and the cases were divided into eosinophilia elevated and non-elevated group according to blood eosinophils, and nasal polyps were evaluated for histopathology eosinophil count. Statistical analysis was performed to compare two groups' pre- and post-operative symptoms of VAS score, sinus computed tomography (CT) scans scores according to the Lund-Mackay system and the outcome of surgery. Both groups' factors that might have affected their outcome were analyzed by t-test, Chi square, Pearson Correlation Coefficient and Willcoxon rank sum test. Results: Seventy two cases were followed up from 24 to 78 months.The average follow-up time was 56 months. The VAS score in the eosinophilia elevated group (n=16) was higher than that in the non-elevated group(n=56), and the difference was statistically significant (11.44±7.13 vs 4.98±5.64, t=3.726, P<0.05). The control of symptoms in the peripheral blood eosinophilia elevated group was less than that in the non-elevated group, and the difference was statistically significant (Z=-1.979, P<0.05). There was a positive correlation between eosinophil counts in peripheral blood and tissues of 72 cases (r=0.429, P<0.05). Conclusion: There is a significant correlation between tissue and blood eosinophil counts, and eosinophilia group has poorer outcomes.