Sphene(CaTiSiO5),a calcium titanosilicate ceramic has been prepared from a powder mixture of CaCO3,TiO2 and SiO2 using vibro-milling for homogenization and activation of precursors.During the high pressure-high temperature synthesis process(at 4 GPa,1200℃)sphene undergoes into phase transition,from room temperature phase P21/a to high temperature phase A2/a.Evidence of that structural phase transition are given in this paper using infrared(IR),Raman spectroscopy and X-ray powder diffraction(XRPD).Microstructure and particle size of both phases were analyzed by scanning electron microscopy(SEM).Coefficient of thermal expansion for the both,high and room temperature phase was examined by dilatometer up to 1200℃.