Objective To investigate effects of X-ray on the structure of cerebral temporal lobe cortex and acetylcholinesterase (AChE) activity of the brain and expression of Bax protein and epidermal growth factor (EGF) of cerebral temporal lobe cortex in filial mice． Methods One hundred and sixty filial mice were irradiated with different dosages (0Gy，1Gy，3Gy，5Gy，7Gy) of X-ray．The AChE activity was detected by colorimetry, expression of Bax protein and EGF of cerebral temporal lobe cortex were measured by immunohistochemistry，and the changes of cerebral temporal lobe cortex were observed by biomicroscopy． Results X-ray affected the development of cerebrum of filial mice． The number of Bax protein immunopositive cells in 1Gy group was lower and that of EGF was higher than that of the control group at the 5th-20th day after irradiation(EM>P/EM>>0.05)， whereas AChE activity was higher than that of the control group(EM>P/EM><0.05)． The number of EGF immunopositive cells and AChE activity in 3Gy group firstly decreased and then increased(EM>P/EM><0.05)，whereas that of Bax protein firstly increased then decreased (P<0.05)．The expression of Bax protein and EGF was strongly positive in 5Gy and 7Gy groups，and the number of their positive cells was higher and AChE activity was lower than that of the control group(EM>P/EM><0.01)．The thickness of temporal lobe cortex decreased and their structure was not clear．Compared with the control group，cell den