Abstract: Objective To access birth sex ratio related factors in Changzhou city,Jiangsu province.Methods We used a random sampling method to choose study population from the city,towns and villages.The infants born during the pe riod from Jan 1,2006 to Dec 31,2008 and their parents were enrolled in the survey.Related factors for birth sex were ana lyzed with logistic regression.Results Of 6 250 infants selected,boys accounted for 52.17%,and girls accounted for 47.83% with a sexratio of 109.10.There sults of logistic multifactor regression showed that boy preference in mothers and fathers was a risk factor of ratio birth(odds ratioOR=2.796,OR=1.644).While girl preference in mothers and fathers was a protective factor(OR=0.680 andO R=0.486).Conclusion Sex ratio is high in Changzhou city.Boy's preference in parents affects birth sex ratio.