Brain aging (dementia) model mice were made by cervical subcutaneous injection of D-galactose solution. Learning and memory abilities were detected with water maze test and superoxide dismulase(SOD) activities and malondiadehyde (MDA) contents in the liver and brain were determined after intragastrical administration of Shenlong Decoction (参龙汤) for 6 weeks. The results indicated that the swimming time was shortened and the correct swimming times increased, SOD activity raised and MDA content decreased in the three Shenlong Decoction groups with different doses as compared with the model group. It is concluded that Shenlong Decoction has the effects of anti-free radical injuries and improving the learning and memory abilities of the brain-aging mice induced by D-galactose. Brain aging (dementia) model mice were made by cervical subcutaneous injection of D-galactose solution. Learning and memory abilities were detected with water maze test and superoxide dismulase(SOD) activities and malondiadehyde (MDA) contents in the liver and brain were determined after Intragastrical administration of Shenlong Decoction (参龙汤) for 6 weeks. The results indicated that the swimming time was shortened and the correct swimming times increased, SOD activity raised and MDA content decreased in the three Shenlong Decoction groups with different doses as compared with the Model group. It is concluded that Shenlong Decoction has the effects of anti-free radical injuries and improving the learning and memory abilities of the brain-aging mice induced by D-galactose.