Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophic family, which promotes neuronal survival and repair during the development and after central nerve system (CNS) injury. This study was aimed to investigate BDNF expressions after fatigue swimming in rats and discussed their neurobiology function of exercise-induced fatigue. Rats were divided into control group (CG) and exercise group (EG); CK&BU were measured to value the animal model setting up. The streptavidin-biotion-peroxidase complex (SABC) method was performed to detect BDNF protein expression in hippocampus and striatum, using optical density (OD) and area density (AD) as two indexes to value the protein expression. After exercise-induced fatigue, cells arrange shows foul-up and loosen in cone district of hippocampus. Some cells crinkle, strut and chip. There are BDNF expression both in hippocampus and striatum in CG and mainly in the cell body; in 24EG expression of BDNF increased significant (P