Abstract: Objective To investigate the natural antibody level of Hib polysaccharide in healthy children in Yancheng city.Methods 543 serum samples from healthy children were collected and the Ig G antibody level of haemophilus influenza type b polysaccharide was measured with enzyme-linked immunosorbent assay.Results The positive rate of antibody to PRP was 47.33% in children less than 14 years old,and there was no significant difference between genders.The antibody level of neonates was the highest,and declined to the lowest in the children of 12 months.The level increased with the age in those older than 1 year and reached the maximum at the age of 10～14 years.Conclusion Immunity antibody level to Hib polysaccharide was not low in Yancheng city.Children aged 3～6 months with the lowest antibody mevel were the high-risk population.