To evaluate the practice of peripheral blood eosinophil in the diagnosis of eosinophilic chronic rhinosinusitis(ECRS).The correlation between eosinophil count and percentage in peripheral blood and that in topic tissue in 787 patients (the first affiliated hospital of Wenzhou medical university, from Jan. 2013 to Jun. 2016) with chronic rhinosinusitis (CRS) were retrospectively analysed. The optimal cutoff value of blood eosinophil count and percentage as predictors for ECRS was determined by receiver operating characteristic curves (ROC) and their diagnostic ability was compared.The positive correlation between eosinophil count and percentage in blood and that in tissue was found respectively in 787 patients with CRS (r=0.450, 0.499, 0.463, 0.465, P<0.01). Although the significant correlation between blood eosinophil count and its count and percentage in tissue was not found after blood leukocyte and tissue eosinophilic inflammation was controlled respectively (r=0.041, P=0.380; r=0.046, P=0.329 and r=0.023, P=0.618; r=0.032, P=0.499), blood eosinophil percentage still showed significant correlation with tissue eosinophil count and percentage, but reduced unequally after that(r=0.383, 0.436 and r=0.153, 0.169, P<0.01). With ROC analysis, the diagnostic ability of optimal cut off values of eosinophil count and percentage varied as the histological criteria for ECRS differed.Eosinophil in peripheral blood showed significant positive correlation with its tissue infiltration, which may be not strong and easily effected by individual factors.Theoretically, blood eosinophil may have a diagnostic significance as a predictor for ECRS but not practically.