Objective To analyze the risk factors associated with allergic disease in preterm infants during the first year of life.To investigate whether there was any association between peripheral blood eosinophils and allergic di-sease during the first year of life benefit of hydrolyzed formula feeding in preterm infants. Methods A nested case-control study was conducted in a cohort of artificial feeding preterm infants admitted to Neonatal Intensive Care Unit, Shanghai Children's Medical Center from January 2012 to April 2013.The preterm infants were monitored from birth up to 1 year of age and the findings were related to development of allergic disease.Individuals with allergic disease during the first year of life(cases) were matched with gender, as previously described with two individuals(controls) who remained event-free during the study.The risk factors associated with allergic disease in preterm infants during the first year of life were analyzed.And whether there was any association between peripheral blood eosinophils and allergic di-sease during the first year of life benefit of a hydrolyzed formula feeding in preterm infants was investigated.Different variables in control and case individuals were compared with t test for normal distribution measurement date, χ2 tests for categorical variables and Mann-Whitney U test for non-normal distribution measurement date, and multiple conditio-nal Logistic regression were used to investigate the risk factors associated with allergic disease in preterm infants. Results Thirty-four individuals were in cases and 68 individuals were in controls.In a conditional multivariable Logistic model, peripheral blood eosinophils of preterm infants at full enteral feeding(EOS-2)(OR=5.941, 95%CI: 1.165-41.375, P 0.05). Conclusions Peripheral blood eosinophils of preterm infants at full enteral feeding EOS-2 and family history of allergy were the 2 independent risk factors for allergic disease in preterm infants during the first year of life.Contrast to individuals fed with standard preterm formula after birth, individuals fed with hydrolyzed formula had lower association between factors of peripheral blood eosinophils and family history of allergy, and allergic disease during the first year of life. Key words: Infant, preterm; Protein hydrolyzed formula; Eosinophils; Allergic disease