Objective\ To detect thrombomodulin protein in 18 weeks human fetal lung. Methods\ SP method was used in the study. Results\ It showed that, in fetal lung tissues, thrombomodulin expressed in the endothelial cells of capillaries surrounding the primary alveoli, but it was absent in cuboid cells and ciliated\|columnary epithelium cells and cartilage. Conclusion\ Our results suggest that thrombomodulin does not exist in middle and late stage's human fetal lung.\;