To study the effect of Boschniakia rossica extract on free radicals in the brain of D-galactose induced senile rats. Sixty Wistar rats were randomly divided into normal group, model group (48 mg.kg(-1).d(-1) D-galactose, SC), Boschniakia rossica group (100, 150, 200 mg/kg ig and 48 mg.kg(-1).d(-1) D-galactose, SC). After 40 days, the activities of SOD, MAO and the content of MDA were measured with colorimetric method, and the histological changes were synchronously observed by electronic microscope. Boschniakia rossica extract significantly increased the SOD activity, decreased the MDA content, and inhibited the MAO activity in the brain tissue. It was observed under microscope that Boschniakia rossica extract could retrieve the degeneration of mitochondrion. Boschniakia rossica extract can clear the free radicals for D-galactose induced senile rats.