Objective To study the morphological changes of lymphatics in transplant tumor of mice. Methods H22 cells were inoculated under the armpit skin of KM mice. Tumor was obtained two weeks after inoculation. HE staining was used to observe the development of tumor. 5'-nase-alpase double staining was performed to observe blood vessels and lymphatics. Ultrastructures of lymphatics were observed with electron-microscopy. Results Tumor occurred in all the mice. Under microscope there was none of lymphatics in the center of the tumor, a few lymphatics and a lot of blood vessels could be seen in periphery of tumor. Under TEM damage of the organelles could be seen in the endothelial cell of lymphatics. Conclusion Neonatal lymphatics can be seen in transplant tumor caused by H22.