Objectives: To study the functions of dental follicle during tooth root development, meanwhile, the developing conditions of tooth germ transplanted to nude mice were observed. Methods: Sixteen five-day-old postnatal Balb/c mice were divided into four groups, four in each were subdivided into two subsections randomly. The first mandibular molar teeth germs were enucleated and dental follicles in half of them were removed. Subsequently, each of the germs was separately transplanted into super muscles of adult nude mice. At 7,14,21,28 days after grafting, the germs were collected, fixed, demineralized, dehydrated, and embedded in wax in sequence. Serial sections of 5um thick were made following the routine methods, stained with haematoxylin-eosin dying solution, and observed under a light microscope. Results: All implants located in the super muscles with abundant capillary vascular without inflammation when they were re-approached to. Under the microscope although all tooth germs could develop further after grafting, the tooth germs without dental follicle seemed develop slower, smaller in size, and lower degree of calcification compared to that of those in virgin status. Limited inflammatory reaction was found from two weeks and on after grafting. Conclusions: The study suggests that the dental follicle plays an important role in tooth development especially in root formation. Supported by Shandong Provincial Excellent Young Scientist Scientific Foundation.02BS096 and National Natural Scientific Foundation of China.30371537.