The characterization of Nb-doped layered perovskite SrBi2Ta2O9 was studied.The mechanism of modification of properties was analyzed.Photoacoustic spectroscopy has been used to study the light absorption of SrBi2Ta2O9 with various Nb contents.The results show that the absorption band at 580nm in the photoacoustic spectroscopy exhibits a red shift with increasing niobium content.The remanent polarization of Nb-doped SrBi2Ta2O9 films depends on the concentration ratio of Ta/Nb.The remanent polarization of the films arose an maximum at the area of Ta/Nb≈1.This may be related to the existence of morphotropic phase boundary.