The pure nanometer powder of Barium Strontium Titanate (BST) was synthesized by the hydrothermal method using the precursors prepared by SolGel method, the precursors of gel with ten percent of TiO2 (anatase) could produce huge number of onedimensional BST by the hydrothermal method with the same hydrothermal condition. The phase structure and morphology of products were characterized by Fourier transform infrared spectrometer（FTIR）and Xray powder diffraction (XRD) and field emission scanning electron microscope (FESEM) and Transmission electron microscopy （TEM）as well as electron diffraction (SAED). The forming mechanism of onedimensional BST was introduced. The results indicated that the growth mechanism of onedimensional BST is the growth of situ.