Objective：To study the effect of Macrophages subtypes in lung injury of hyperoxia-exposed newborn rats. Methods：sixty-four newborn SD rats were randomized into two groups：air-exposed group (the control group) and hyperoxia-exposed group (the high oxygen group)．The rats in high oxygen group were placed in a sealed Plexiglas chamber maintaining 02 1evels above 95％ and those in control group were exposed to air. All rats were euthanized 7d later. Statistical analysis was carried out on the newborn mice weight. Adopting the flow cell technique with different antigen of three kinds of macrophages (classic activated macrophages, and wound-healing macrophages, regulatory macrophages) for different periods of macrophages double positive screening. The value of lung damage score calculated with histology under light microscope．Results：There were significant differences among two groups in the fields of lung damage score (P<0.05). Compared with the control group, the expression of F4/80 increased in high oxygen group (P<0.05), the expression of IL-12 increased in high oxygen group at each time point (P<0.05), the expression of CD163 increased in high oxygen group at 1st day, 7st day, 21st day (P<0.05), which has no statistical difference at 3st day (P>0.05), the expression of IL-10 increased in high oxygen group at 1st day, 3st day, 7st day(P<0.05), which has no statistical difference at 21st day (P>0.05). Conclusions：Macrophages subtypes were existed in lung injury of hyperoxia-exposed newborn rats.