The irradiation damage of Chinemys reevesii's brain cells were studied by transmission electron microscope and flow cytometry on the basis of cell culture.Under the transmission electron microscope,the unirradiated brain cells were difform and had prominency spread.The karyons were geometry shape or elliptic.The nucleolus and the gap of peri-nucleus were clear.The stroma electronic density was uniform and the structure of inner crista was clear in mitochondrion.The endoplasmic reticulum was eidetic.The cytoplasm was uniform and many glycogen particles appeared in cytoplasm.When the brain cells were irradiated,the fragments were increased outside the cells.The visible sublobe appeared in karyon,and the nuclear fragment was seen.The chromatin was pycnosis and focused in nuclear fringe.The vacuolizations were seen in mitochondria,endoplasmic reticulum and partial cytoplasm.The apoptosis body appeared.The detected result of flow cytometry showed that the great mass of cells in unirradiated group and in irradiated group were in G₀/G₁ stage,which took up 61.9% and 59.7% respectively of the total of detected cells.Ahead the major peak,the peak of apoptosis appeared in the irradiated group cells.In the G₂/M stage,the cell numbers of the irradiated group were fewer than those of the unirradiated group.The results showed that the apoptosis occurred in C.reevesii's brain cells when the cells were irradiated.