Abstract: Objective To investigate the effects of tumor necrosis factor α (TNFα) on proliferation, apoptosis of mouse adrenal cortex cell lines Y1. Methods The mouse adrenal cortex cell lines Y1 were treated with TNFα of different concentration during different duration. The cells proliferation was tested by MTT assay as well as cytostasis was detectd by Trypan Blue Coloring Method. Flow cytometer was used to observe the cells apoptosis level. The changes of Caspase8/3 of the cells were detected by spectrophotometry. Results After being treated with TNFα of different concentration during different duration, reproductive activities of Y1 cells were significantly inhibited (P＜0.05); the apoptosis and Caspase8/3 levels of Y1 cells were both remarkably highered (P＜0.05). Conclusion TNFα can inhibit proliferation of Y1 cells, promote their apoptosis, and increase their Caspase8/3 activities to inducing the apotosis.