3,3',4,4'-Biphenyl tetra carboxylic diandhydride, 4,4'- oxydianiline and AgNO3 were used to syn. thesis polyimide nanofiber with silver through two steps by electrospinning. The structure and morphology of nanofibers were studied by X-ray diffraction( XRD), transmission electron microscope( TEM) and scanning electron microscopy( SEM). The antimicrobial activity of polyimide( PI) and polyimide containing silver ( PI/ Ag) were researched through impregnation method. The results showed that silver's crystal structure appeared in polyimide matrix, and silver particles, which average diameters were about 10 nm, dispersed uniformly on polyimide surface. The antimicrobial activities of PI/ Ag nanofiber against E. coli, S. aureus and B. subtilis illustrated excellent effect and the best antibacterial rate up to 99. 1%. This study may provide a new insight for polyimide applied in biomedical materials and other applications with good thermal performance and antibacterial property.