Abstract: Objective To elucidute the effects of all-trans-retinoic acid(ATRA) on bladder cancer cell line T24 and to establish the cell apoptosis model. Methods Growth inhibition was detected by MTT assay Morphological evaluation of apoptosis were studied by phase contrast microscopy fluorescence microscopy and transmission election microscopy.Analysis of DNA fragmentation was examined agarose gel eletrophoresis and by flow cytometry. Results Either3×10-5M or 3×10-6M ATRA can suppress cell growth and induce typicall hallmarks of apoptosis after treating the cells for 6 days, the percentage of apoptosis cell of 3×10-5M，3×10-6M ATRA and control group was 20.16%，15.31% and 1.49% respectively on flow cytometry.A charactristic DNA “Ladder”on agarose gels was appeared in treated group. Conclusion ATRA significantly decreased T24 cell proliferation in a dose-dependent pattern ATRA may induce sufficient apoptosis of human bladder cacer cell line T24.