The title nanocrystalline powders were prepared by sol-gel method, the influences of grain size on crystal structure were investigated by XRD and DSC techniques. The experiment results show that the tetragonal ferroelectric phase content of the powders and the Curie temperature Tc are increased with the increase of grain size. When the grain size is less than 34. 7nm, crystal structure of the particle changes into cubic paraelectric phase and the transition of ferro-paraelectric phase disappears as well. The title results nanocrystalline powders were prepared by sol-gel method, the influences of grain size on crystal structure were investigated by XRD and DSC techniques. The experiment results show that the tetragonal ferroelectric phase content of the powders and the Curie temperature Tc are increased with the increase of grain size. When the grain size is less than 34. 7nm, crystal structure of the particle changes into cubic paraelectric phase and the transition of ferro-paraelectric phase disappears as well.