The ceramics with the formula of Sr1-xSm2x/3TiO3 (x=0-0.5) were prepared by conventional ceramic process. A single phase of SrTiO3-type with cubic perovskite structure was found companied with a decrease in crystal volume when x<0.5, which was confirmed by X-ray diffraction results and Rietveld refine. At the level of x=0.5, the sample consisted of two phases of SrTiO3-type and Sm2Ti2O7. Raman spectra were used to confirm the change of vibration to explain the variation in microwave dielectric properties. The dielectric constant decreased, the quality factor increased, and the temperature coefficient shifted negatively, when the x value increased from 0 to 0.4. When the x value located between 0.3 and 0.4, the ceramics exhibited high dielectric constant of 140-152, high quality factor (>6000).