Abstract: Objective To investigate the effects of selenium on neuron and mitochondria of senile mice.Methods Using D-galactose induced aging model,the activities of SOD,GSH-Px,MAO-B and levels of MDA,GSH in brain were measured.The changes of LPF and mitochondria were observed by using transmission electr on microscope.Results Selenium can obviously enhance the activities of SOD and GSH-Px,increase the level of GSH,decrease the levels of LPF and MDA,inhabit the activity of MAO and protect the mitochondria from being destroyed.Conclusion Selenium can raise the antioxidation ability of mouse brain and delay the aging of neuron and mitocho ndria.