Abstract: Objective To investigate the level of poliomyelitis antibody among preschool age children,and evaluate the effect of polio immunization. Methods Seven age groups among 0 to 7 years children were sampled by the systematic sampling method in 16 counties in Anhui,and 1 754 serum samples were collected.Microplate neutralization test was used to determine antibody level. Results All of subjects had immunization records while 96.41% of them were 3-5 times.The rates of neutralized antibodies positive to Ⅰ,Ⅱ and Ⅲ were 99.43%,99.20% and 98.86%,respectively.The geometric mean titers(GMT) toⅠ,Ⅱ and Ⅲ were 1∶193.40,1∶117.26 and 1∶85.03,respectively.98.29% of the subjects were all positive inⅠ,Ⅱ and Ⅲ.Both positive rate and GMT between each serotype had significant differences(P<0.01).The positive rates of each serotype were above 97% in all age groups.For GMTs,not like positive rates(P>0.05),a trend of decreasing with increasing age was presented(P<0.05).The positive rates of different regions as south of Anhui,middle of Anhui,north of Anhui were all above 98% but without significant differences(P>0.05).Antibody levels between different regions have significant differences (P＞0.05,except F_Ⅱ).The results of multiple-factors analysis showed that the GMTs were significantly associated with age,region and the result of all positive in each serotype(P<0.01). Conclusion In preschool age childre in Anhui,the positive rate of poliomyelitis antibody and GMTs are still maintaining a high level,and a stable immunization barrier has been established by polio immunization.