Abstract: Objective To identify the temporal-spatial expression of B7 family co-inhibitory molecules during lung development, and to explore the roles of B7 family co-inhibitory molecules in the developmental process of pulmonary regional immunity. Methods The expression of B7 family co-inhibitory molecules (B7-1, B7-2, B7-H1, B7-DC） in different developmental stages of Rhesus monkey lungs were normalized and calculated by the reads per kilo-base of transcript per million mapped reads (RPKM) method. Immunohistochemical staining was performed to identify the localization and the protein of B7 family co-inhibitory molecules in different developmental phase (canalicular stage, cystic stage, alveolar stage) in mouse. Results The expression of B7 family co-inhibitory molecules in rhesus monkey were increased during the prenatal period (cystic stage, alveolar stage), the expressions of B7-2 and B7-H1 mRNA were significantly increased in alveolar stage (P<0.05). The results of immuno-histochemistry indicated that B7 family co-inhibitory molecules were mainly expressed in airway epithelial cells, and their protein levels were increased during the prenatal period. The expressions of B7-2, B7-H1 and B7-DC were significantly increased from canalicular stage (P<0.05). The protein of B7-2 was higher in airway than that in bronchus (P<0.05).Conclusion B7 family co-inhibitory molecules are mainly expressed in airway epithelial cells, and the expressions are increased during the prenatal period, which suggests that B7 family co-inhibitory molecules are involved possibly in the development of pulmonary regional immunity.