Objective: To investigate the differentiation-inducing effects of all-trans-retinoic (ATRA) to HPV16 subgenesimmortalized human endocervical cells (H8 cell) in vitro. Methods: HPV16 subgenes-immortalized human endocervical cells(H8 cells) were cultured in vitro. After treated with ATRA, the proliferation of immortalized human endocervical cells was measured by MTT assay; morphological changes were observed using M and TEM; cell cycle was analyzed by FCM;expression of Ki67 was tested using immunocytochemistry and the activity of telomerase was tested using PCR-ELISA.Results: ATRA could inhibit proliferation of H8 cells significantly and induce their morphodifferentiation. According to FCM, H8 cells accumulated in G1 phase and expression of Ki67 and activity of telomerase reduced significantly after treatment with ATRA. Conclusion: ATRA could induce the differentiation of H8 cell line obviously, which might be achieved by inhibiting proliferation, blocking cell cycle, and reducing activity of telomerase.