Objective  To study the express of HBsAg in the pulmonic tissue of the dead fetus infected by HBV by maternal  fetal transmission.Methods  Pulmonic tissue of 40 dead fetus deherated by puerpera with hepatitis virus B was co~llected.To detect HBsAg by immunocytochemistry(SP).Investigated the results of detection on HBV in the mother veins before deli~very.Results  There were HBsAg in the pulmonic tissue.They were mainly on the alveolar sac,alveolar duct,bronchiole and in the alveolar cells plasma,pulmonic vessel.They were not in the alveolar cells nuclei.The positive cells were single or in clusters form distributed over the pulmonic tissue.There were significant difference(  P  <0.05)for the comparison between the rate of the HBsAg positive express,alveolar cells degeneration and amniotic embolism in the pulmonic tissue of the dead fetus that the puerpera deherated with hepatitis virus B for only one of ①HBVM+,②(HBsAg+HBeAb+HBcAb) and③ (  HBsAg+  HBeAg+HBcAb) in the mother veins before delivery.The difference of the comparison between①and ② was not significant(  P  >0.05).Conclusion  It was the more risk factor of HBsAg express in the pulmonic tissue of the dead fetus infected by HBV by maternal  fetal transmission that HBVM(HBsAg+HBeAg+HBcAb)was positive in the mother veins before delivery.