Abstract: Objective To examine the relationship between breastfeeding and the sociality performance among 12-month-old infants.Methods Totally 1 943 infants aged 3 months±7days who received child health care at Care Department of Maternal and Child Health Center between January and December,2012 were recruited and followed-up.The sociality performance of the infants was regularly evaluated by a self-desinged questionnaire.The information on socio-demographic factors,perinatal factors and monthly breastfeeding were collected.Results After adjusting for demographics and perinatal factors in logistic regression,exclusive breastfeeding at 2,3,4,5 month of the age was a promoting factor for sociality performance of the 12-month-old infants,with the odds ratios(ORs)of 1.384(95%confidence interval95%CI:1.086-1.765),1.279(1.023-1.599),1.361(1.023-1.599),and 1.461(1.043-2.046),respectively.The infants who were partially breastfed between the age of 5-month through the age of 11-month had significantly higher score of sociality performance compared to those of the infants with formula feeding,with the ORs of 1.378(95%CI:1.139-1.668),1.297(1.086-1.551),1.265(1.066-1.501),1.225(1.036-1.447),1.183(1.000-1.398),1.214(1.021-1.442),and 1.269(1.055-1.527),respectively.Conclusion Exclusively breastfeeding at least 2 or more months and partially breastfeeding for more than 5 months have a positive effect on the sociality development of the infants.