Objective：To investigate the expression and clinical significance of CD34，COLⅠ and CXCR4 in bronchopulmonary dys－plasia（BPD）. Methods：Expressions of CD34，COLⅠ and CXCR4 in peripheral blood from 44 premature infants with BPD on the 1st，3rd，5th，7th and 28th d after birth were measured by flow cytometry（FCM） and the expression differences of CD34，COL I，CXCR4 between BPD group and the non- BPD group were compared. Results：On the 1st d after birth，the expression of CXCR4 increased greatly in BPD group compared with that of non-BPD group. With the increase of days after birth，COLⅠlevel peaked on 28th d in BPD group，while CD34 and CXCR4 levels reduced to the lowest. Data of ANOVA for repeated measurement showed that time and the changes in CD34，COL I and CXCR4 levels caused an interactive effect on the occurrence of BPD（F=77.66，P=0.000）. ROC curve displayed that area under the curve of COL I was 0.867，higher than those of CD34 and CXCR4. When COL I was 1.3%，the sensitivity was 69.7% and specificity was 86%. There were statistically significances in BPD group among different time points（P=0.000）. Conclusion：Circulating fibrocytes with increased level of COLⅠas well as decreased level of CD34 and CXCR4 are closely related with the occurrence of BPD.