Abstract: Objective To investigate the changes of cell membrane,ultrastructure,cell cycle and the apoptosis rate in PC12 cells after microwaver adiation.Methods The PC12 cells in logarithmic growth period of 6~7 d were induced with nerve growth factor for 7~10 d.Then the cells were exposed to microwave at average power densities of 0,10,30 and 50mW/cm² respectively.The PC12 cell membrane,ultrastructure,cell cycle and the apoptosis rate were studied by means of atomic force microscope,transmission electron microscope,flow cytometry and laser scanning confocal microscope.Results After 30 and 50 mW/cm² microwave exposure,there were more cells in G₀-G₁ phase and no change after exposure to 10 mW/cm² radition.In the 30 mW/cm² group,apoptosis rate was significantly higher(P<0.01)and necrosis rate was no change.Cells with their regular nucleus,chromatin concentration,nucleus intermembrance space widen,mitochondrias welling and cavitation,rough endoplasmic reticulum expanding were observed.The membrane of PC12 cells was rough and there were some round or irregular holes.Conclusion 30 mW/cm² microw ave radiation may induced PC12 cell injury,cause the blockage of cell cycles,cell apoptosis,the abnormal ultrastructure and membrane perforation.